Voltmeter check of the gas valve

[@richardcote9663]

At 4:45 you mention some integrated boards sense if the valve is unplugged. That is a gold nugget of information my friend. Thank you. I was scratching my head and almost condemned my gas valve. Haven't found another video that mentions this. Turned out to be a bad connection on the integrated control board at the 9 way plug. I realize this video is 10 years old. Nice job man.

[@behatchithetooler6912]

Thank you very much. My pool heater was down for 2 seasons, I suspected the gas valve, but I was not certain, and did not want to spend the $250 for a new one. I performed this test with a multi meter and became 100 percent certain that it was my gas valve. Replaced the gas valve and the heater now works again. Thank you!!!!

[@grayfurnaceman]

Welcome GFM

[@fullcircle.organics]

The most helpful videos and written tutorials I have found! Super concise and clear descriptions. Thank you!

[@theoldman443]

I have watched all of the content you posted on the Lennox furnace and this is where I found a problem.

[@raquelsapalaran2907]

Good tutorial very informative and easy to understand, thank you for sharing your knowledge.

[@bonafide6464]

Lennox 80UHG. Check the wire connection from the gas valve to the wire harness on the board! Thank you Furnace Jedi! You are the best, bar none. Listen to this episode. My igniter came on but gas valve switch didn’t kick on. It was replaced 2 years ago so had doubts it was the valve switch. I checked voltage coming into the switch as you described in the video. It measured 12 volts. What the heck? I measured it 3 times still 12v. I measured the voltage coming out of the transformer, I got 24v. Hmmm. I followed the two wires from the gas valve, they are blue and yellow, and they connect to a wire harness on the control board. There is a blue and yellow wire coming from the transformer to the same wire harness. So I jiggle and press the wires into the harness real good. They are dusty and stiff with age. I flip the power switch on to the furnace, it cycles, igniter glows hot then I hear the gas valve click on and wow it fires up! I’ll be damned bad wire connection! So far it seems to be working fine. Still amiss how I was getting only 12 volts and not the full 24 from bad connection but o well it’s working! I did replace the pressure switch but don’t think that was the problem. I’m gonna put the old one back on and see if it’s still good. From what I’ve read if the pressure switch was bad the igniter would not have turned on. Thank you! Thank you!

[@fullofbullets58]

by the way, your videos are top notch

[@tykesplace]

Thanks for taking the time end effort to make these videos. They're very informative and easy to follow. I found this one because of an issue I'm having on my Goodman 080-4 2-stage furnace. It seems like there's a short in the connector to the solenoid. When it calls for heat, but solenoid doesn't trip, I can put very slight sideways pressure on the connector and it trips. If the HSI is still hot then the burners fire. Bump the connector again and gas shuts off. Following you procedure here I check voltage and at call for heat I have 25.6 V~. I pulled the connector board and housing like you show in one of your other videos. The board looks good.No burns or breaks. I have continuity from the wire side of the connector, and the various spots on the board that I can trace them too. I'm wondering if it might be as simple as the sockets in the molex connector being loose. I have a new valve on the way, on the assumption it's a shorted connector or board. Thanks again!

[@grayfurnaceman]

+tykesplace It could be the connector. Or it could be a solder connection on the board is "haloed". GFM

[@jonascourtney5999]

Great video, I have the one you can not ohm, I am tracking a code 7 on a Trane 90 series furnace 10 years old. The only thing I notice is that voltage fluctuates, but does not goes bellow 23 Vac and I can read amperage with the plug on, at least as I have the furnace cover open. I suspect cold solder cracks on the board to the multi wire connector that act up after gets warm; wire is okay, tested okay, so I leading towards a problem with the IFC board.

[@royhudson8416]

On Goodman gas/ac unit….I am getting briefly way higher voltage than 27v….more like 160v. Think my pc board is bad?

[@anastasiabauer2959]

follow up question: when voltage come across the 36G24-618 valve, I hear a click then nothing (no gas). Is the click indicating the valve is opened or is that just voltage going into the solenoid? thank you again.

[@theoldman443]

When I hooked the meter to the wires that you show and I let the furnace run its course the first voltage reading was 18.4 second 12 volts and the third was 11.6. What might cause this? I’m sure those are not ghost readings as they only read when the furnace goose through it start up sequence. Thank you for being so quick on replying....

[@grayfurnaceman]

Unless you are getting 24 to 28 volts, it is a ghost voltage. GFM

[@bernardocisneros4402]

Are all these valves 24 volts DC or are some of them actually 24 volts AC? I just took out a Robertshaw from my parent's home because it failed after 41 years of service (they got their money's worth and then some) and I took off the plastic cover on top of the valve and underneath it was a circuit board with 2 diodes. I removed 3 screws holding the circuit board, pulled it off the valve, and there were 2 terminals on top of the valve. I applied 28V AC to the to terminals and got nothing, but when I applied 25V DC (2 car batteries in series) the solenoid clicked nicely everytime I applied the 25V, so it's a nominal 24V DC solenoid but uses the 2 diodes to rectify the 28V AC.

[@rivernet62]

24V AC???

[@bernardocisneros4402]

@rivernet62 The one I took out of my parent's furnace is 24V DC but it has 2 diodes to rectify the AC to DC

[@realSamAndrew]

If the gas valve is working and the furnace lights and operates for a full cycle, will there be a constant 24v to the gas valve as long as it's running? Or does it only energize for a moment to open it and energize again to close it? In other words, is the valve only open for as long as it has power, like a contactor?

[@grayfurnaceman]

It must have power to stay open. GFM

[@remscurvo]

To clarify, does the HSI need to heat up first and at a certain temperature send a signal to the furnace or ignition control which then energizes the gas valve? Or is there simply a timer or delay built into the control once the HSI is energized than the gas valve is energized for the trial for ignition? I believe in a few of your other videos, even if the HSI does not glow, the gas valve still energizes and goes through a trial for ignition. You actually listen for it as part of troubleshooting the HSI. Thanks again for the videos.

[@grayfurnaceman]

There is no temp sense. Its simply a timer. We know how long the ignitor takes to warm to temp. So the timer lets the time go by, then opens the gas valve for a trial for ignition. The control has no idea if the HSI is warming(there are some that monitor amp draw of the HSI and blink a code for that). But most do not. So the gas valve will come on but if there is no flame sensed, it does not stay on longer than a few seconds. Hope this helps. GFM

[@remscurvo]

grayfurnaceman Thanks for the clear explanation.

[@dimas883]

I tested the gas valve as you discussed but I have 14 volts ac before the furnace calls for gas. when the furnace calls for gas the volts go up to 24v. is it normal to have 14v at the gas valve before the furnace calls for gas? thank you

[@Murph3867]

Probably a backfeed, this happens with high voltage on some blower motors and even heat strips for me

[@edbrandt8972]

I don't get 24 volts AC after the ignitor glows. Less than 0.9 volts AC. I ordered a new control board. Maybe it's a bad solder connection? I have not looked yet.

[@sabergermd]

In automotive electrical diagnosis we often back probe connectors to see what is happening while modules are running. Can you do that with the gas valve to avoid the issue of continuity?

[@Johnny-310]

Omg your videos are so helpful I'm going to share you videos

[@grayfurnaceman]

Thanks for the support. GFM

[@eloy09]

Why i’m getting 40v? Could be that one of the issues?

[@TheWickwire007]

Your videos are great and very clear thank you very much.

[@oldwortex5818]

Need some help. 14 years old furnace. Worked fine until about 2-3 weeks ago. It was not coming on, so I started checking. I had 24v at the time when the igniter was glowing but no flames. I wiggled the solenoid and it started working. My happiness was short lived, it stopped after a few days. I checked wires, etc. and again the 24v, all seemed good. I took the solenoid out and cleaned the inside under the coil, on the shaft. All seemed ok, so I put it back and unit started working again. For a week. Now its been dead. So I bought a new gas valve. Same part # and installed it today. I still have the 24v at the time the igniter is glowing, but still no flames. Gas is on, bill is paid, the 2nd floor unit and water heater also works just fine. I'm puzzled what could be the issue. I turned all other unit valves off (knob on the gas line) and tried, no luck. Unit is 16 years old but we are in SC so the heater isn't running a lot. Maybe about 2-3 months a year. So this 14 year old unit is about as much used as a 4 year old NH unit. What could be the issue ? I don't have an equipment to measure gas pressure, but what would cause the gas pressure to drop suddenly and not in a past 14years, and why would all other units on the same line work perfectly fine ? There is no cracks or bends in the gas line, nothing is changed since it was running fine. I put in a new igniter and flame sensor to make sure its all good, of course it did nothing. I also swapped the fan with the 2nd story unit, not because it was not working but because it was making a little bearing noise. I did that about a week ago when it was working and loved the quiet operation. We only use the 1st floor unit as heat rises and we keep the bedrooms door open. The 2nd floor unit ran very little in the past 14 years. What to do ? Please, I need help. In about 2 days it will drop to 23F here so I want to make sure we have heat.

[@EurekaRecycler]

if it has amp draw than does that mean the valve is bad? Can I jump the gas valve with 24v to test it? Thank you

[@grayfurnaceman]

If it has amp draw, the gas valve solenoid is energizing. This test verifies that power is available to the gas valve. It does not mean the gas valve is opening or gas is available. Happy new year GFM

[@djpreemow]

if i do get the 24 volts at the gas valve but only for about 1 second to 2 seconds what should i be looking at? sequence is normal, gas pressure before it is good and hsi lights up nicely. Looks like whoever installed transformer didnt mount it properly and it sheared off at the 24 volts side, common was still attached. kinda leaning towards board..

[@theoldman443]

So when I hook to the wires you show and turn up the thermostat when the furnace try’s to run like in your video that’s the readings I got. I’m not sure what the next thing to check would be

[@grayfurnaceman]

Does the inducer fan start? GFM

[@stephenbarry1253]

Hi thanks for the videos! So I have a Goodman Furnace ~15 years old . Blower good, pressure switch good, Ignitor gets hot, cleaned the flame sensor, 26 volts goes to the gas valve, amp clamp shows a current draw during the 4 sec call for ignition sequence, So likely not a control board issue. And there are no fault codes (solid red) . Can the gas valve still be bad if it is drawing power? Is there anything else it could be or I could check, or am I at the stage of buying a new gas valve? And yes the gas line is on and working.

[@grayfurnaceman]

If the gas valve is drawing power (amp draw at the gas valve), and gas is available, the gas valve has failed. Let me know the results. GFM

[@stephenbarry1253]

@@grayfurnaceman thank you...gonna order another valve.

[@stephenbarry1253]

@@grayfurnaceman any hints on taking off (or putting on for that matter (pipe wrench or just use the leverage from the pipe itself?)) the down stream manifold pipe?: It is stuck on the old valve pretty well. I ordered a new one because I'm sure I'm gonna damage the old one getting it off. Also, is it necessary to do any checks other than for leaking gas after the install? Pressure etc? Thanks again for the quick replys!

[@grayfurnaceman]

@@stephenbarry1253 Use a backup wrench to avoid damage to the manifold assembly. I have done a video about changing a gas valve and doing the things necessary to make it work properly: kzbin.info/www/bejne/nWnNfn1_d7uFfdE Hope it helps. GFM

[@russdewolfe]

I am getting about 24v to gas valve, but the voltage goes up slowly, and seems to not get high enough until the hot surface igniter has already turned off. If I run a jumper from R and C and touch it to the gas valve after the hot surface igniter comes on, it does work. Is this a board issue for sure?

[@grayfurnaceman]

I would also go for the board. GFM

[@alsdock]

Thank you so much for sharing your knowledge and presenting this video. My Bryant 90+ will not light nor "click" although the induction fan and ignitor glows. It tried 3 or 4 times then shut down. I connected the voltmeter and repeated the measuring but no voltage was observed, which leads me to believe the board is bad. Do you concur? Is there a method to verify the board is no good?

[@grayfurnaceman]

Not enough info. The gas valve is only energized for 4 to 7 seconds after the ignitor has warmed. Are you sure gas is available? Gas cock open, gas bill paid? GFM

[@alsdock]

Yes. Gas is supplied. All cocks are open. The furnace worked great last winter. I know the thermostat is functioning.correctly. The starting sequence seems to work correctly.. I attached volt meter leads to terminals of gas valve but no voltage even though the glow was noted at least 3 times.the usual click during ignition just before the burners fire didn't occur.. I verified pressure switch functioned, drain wasn't clogged and flame sensor was cleaned.

[@grayfurnaceman]

If there is no voltage to the gas valve during the trial for ignition, then you have a problem with the wiring to the control board or the board has failed. GFM

[@404-e5b]

thanks! learned quite a bit with this. Ever heard of a furnace that wont lock it self out after multiple failed ignitions? I have seen my home furnace run the induction motor for hours while it keeps trying to cycle for ignitions. No error codes. It just keeps trying and trying. I got it cleaned up and its working fine, but that really has me curious if you have heard of that kind of problem?

[@grayfurnaceman]

Yes. Most units made in the last 25 years will try 3 times, then it locks out. One hour later, it will try again. If it operates as you have described, the control board has failed. Hope this helps. GFM

[@404-e5b]

grayfurnaceman Thanks for the prompt reply! :)

[@404-e5b]

Hi! back again... Furnace was working fine so I never got around to changing the board and summer went well withno issues on cooling... . Problem is happening again this year. all goes well but no ignition, no errors. :( This time I want to attempt checking if the valve is actually getting current. Is that AC or DC the multi-meter needs to be set at? (im more familiar with vehicle wiring but being that its coming from a circuit board, i'm under the assumption it will be DC going to the valve...?) And looking at the video you have red on common ? And black on positive / red wire? Im curious of your multimeter settings to avoid a mistake.

[@grayfurnaceman]

It is A/C going to the valve. The polarity of the leads is not important. GFM

[@404-e5b]

Thank you so much for sharing knowledge. This all comes at a time when my financial resources are very limited so anything i learn to do helps my family. Update: I hooked up the multimeter on a/c mode to the two leads and it flickered to "0240" for a half second just after the igniter started glowing strong. Leads were attached to the valve assembly. I don't know if my multimeter is slow on refreshing but it does not hold the voltage no where near 4 seconds. :( I hear no tick from the gas valve. Q) is there a way to feed the valve 24v directly for testing? to see if it clickcs / hisses? If the valve triggers that will tell me for certain the board is bad and valve is good. But then what if the valve has a short in it. Could that be why i only see a very fast burst of 24? I'm suspecting board since it does not lock it self out nor gives any error codes. all it does is cycle over and over and over...

[@anastasiabauer2959]

I have a White Roger 36G24-618 and I have 24VAC coming across it but it isn't letting out gas once the igniter is on. Can I slightly loosen the boss plug on the gas inlet side and check for gas to check if the gas is available there? Also if the valve needs to be replaced, can I replace it with the 36J24-614 single stage valve? I see dual stage compatible 36J24-614 valve on White Roger website. My worry is the cabling on the 36J which has 6 prongs instead of 2 for 36G. Thank you,

[@grayfurnaceman]

You can but of course be careful and not loosen it too much. There is little difference between the J and the G valves. I can't say I see where the wiring for the J and G models are any different. Hope this helps. GFM

[@anthonynowlan5137]

I have a LP furnace up north. my problem is the electronic ignite for pilot keeps running even after pilot flame is lit. it will not sense this so it will not open main gas valve to fire main burners. although I can move a few wires going to Honeywell controller and get it to sense and sometimes open main valve.? controlleror or possible sensor to electronic pilot ignitor??? what do you think.

[@grayfurnaceman]

ANTHONY NOWLAN I would try cleaning the flame rod if it has one on the pilot. GFM

[@larrykraut1182]

I can here the gas valve click on but I don't get any gas ignition even though my igniter is glowing? Do I need a new gas valve or is there something I can do to make the gas valve deliver gas to the burner?

[@grayfurnaceman]

Do you have gas supply? Other gas appliances operate? GFM

[@larrykraut1182]

@@grayfurnaceman Yes, I have gas supply. The furnace was firing up periodically prebiously. Sometimes it would fire up as normal, and sometimes it would go through the same cycle but would not ignite. Now it goes through the complete cycle and never ignites.

[@grayfurnaceman]

@@larrykraut1182 If you have amperage draw to the gas valve as checked by a clamp meter during a trial for ignition and no gas flow, gas valve has failed. GFM

[@larrykraut1182]

@@grayfurnaceman I don't have a meter, but I do hear the gas valve click on. Would the gas valve click on if I didn't have power to it. If it is the gas valve is there any thing I can do to repair it or do I have to replace it? I intend to replace this old furnace when I can. I don't want to put any more money into it. I replaced the motherboard last year. Thank You.

[@grayfurnaceman]

@@larrykraut1182 If it clicks and gas does not flow, the valve has failed. To be sure gas is not flowing, when the gas valve clicks have a lit fireplace match inserted near the outlet of the burners. If it lights, the hot surface ignitor may be failing by not getting hot enough. GFM

[@FrankDoesIt]

Im only getting 18 volts to the gas valve... should this voltage operate the gas valve?

[@grayfurnaceman]

franktha4th No. The minimum should be about 23 volts. Remember, the voltage can only be read during a trial for ignition. Your voltage sounds like a ghost voltage. A ghost voltage is feed thru from the electronics of the board. This one sounds like a board problem. GFM

[@FrankDoesIt]

ok thank you very much!

[@Kaibil66]

You are the best

[@tommyz1052]

I am Troubleshooting a pool heater, it has a similar control board. Im getting Ac power for a few seconds but its not 24. It seems all over the place for a few seconds then shutsdown. goes up high to almost 100 then 24ac then off. I have a Robertshaw sp715a ignition control board.

[@grayfurnaceman]

Sounds like you may have a short in the low voltage. No simple answer. Just have to start eliminating parts. GFM

[@tommyz1052]

so what feels good is that if I put 24v to M/v from the transformer everything starts up. Gas starts then lights . I had a scheduled power outage , but it was unusual as we have a brownout then surge mid event. The surger It tripped m y AC unit breaker, all the GFI's in the house. Weeks later i find my poolheater wont start. watching your videos , i see sensors are good. Board at startup gives voltage that my cheap meters cant interpret , then to zero. I wonder if its giving the 24 or there is something in the board broken. At this point , parts work and burner stays light if i give it 24v directly to M/V. Should i jump to replacing the board? Also transformer seems blown. Im not a professional and I could have done it in my testing just as I made my findings it seem to stop working. I plan to replace that with a 24v transformer with a breaker.

[@Steve-og3cr]

I did this same check, but the reading was 12v/random voltage instead of 24....then I restarted a few times, it went back to 24v and everything fired up. It's been very intermittent. Jumped the limit sensor, not that. Seems weird a board would be intermittent but I can tell the gas valve won't click.

[@grayfurnaceman]

Your 12 volt reading is a ghost voltage. The board has failed. GFM

[@Steve-og3cr]

@@grayfurnaceman that is my feeling as well. Especially since it wouldn't fire while doing random 12v ish readings. Once I power cycled a few times and got 24-28v and hooked the leads back up, it fired right up! I keep a spare board/Gvalve/limit/flame sensor on standby. Will change board tonight. Cross fingers lol

[@MrZmullen]

Love your videos! They help so much. I have a older modular home with propane furnace. Surface igniter comes on, I get flame and goes out. 3 blinks on the light for ignition failure. Any ideas? Thanks Zach

[@calgaryscluelessdrivers1794]

Great video, but I do have questions. 1) I am not sure where to connect my multimeter. I noticed you connected the multimeter to the middle and right of the plug. Should I connect the red/black lead to HI, C, or PM? 2) Would every gas valve with a plug have the same letters? HI, C and PM?

[@grayfurnaceman]

Ben D Welcome to HVAC. Nothing is the same. C is usually common. Do you have a single stage or 2 stage furnace? GFM

[@reddog907]

The black lead from the meter should be on common and use the red lead on either of the other wires , HI or PM.

[@remscurvo]

Thanks. If there is voltage to the gas valve, how do we determine if the valve is at fault? If I remember correctly, in another video, you mention that a continuity check does not work on most valves. If using ohms is the answer, how do we know the ohms value of a "good" gas valve to compare the readings?

[@bills6946]

If you got momentary voltage at the valve and didn’t get ignition, the valve is bad.

[@markfothebeast]

I'm getting 15v at all times. Than it jumps up to 24v to open the valve. Is this supposed to happen? Is a relay shorted?

[@billbrigham9959]

Very interesting, mine was doing the same thing but not working, no gas flowing. I removed the switch box from the valve assemble and sure enough, one of the power input pins on the board, appeared broken. I resoldered all four joints and Bham, Gas valve now opens and furnace fires up, works. Oddly enough, the voltage to the valve is no longer 15v ac and 27 v ac when on, but rather ov ac and 27v ac when on. Good luck

[@kylewells6871]

Let's say I'm getting 15v to the gas valve prior to firing and once gas valve closes I'm get 27v, is that phantom voltage and could that burn up the gas valve?

[@grayfurnaceman]

The 15 volts is phantom and will not damage the valve. GFM

[@bluwng]

Was this Vac?

[@cliffontheroad]

when U get 10% down votes, it does not mean you do not know the stuff but that it is a bad tutorial. I can enjoy watching a DIY build a deck or a house, but its not a tuitorial. BTW, I've concluded everything can be built in an hour. :) Actually, 1K votes out of an impressive 325K views is a lot of "no opinions." I've liked some of your other stuff. The comments below prove your effort has been appreciated. I also see questions from years ago which drew zero answers. Shame.

[@grayfurnaceman]

The zero answers has always been a mystery to me. I answer almost all comments that are asking for help. Yet, I sometimes look at comments and find some that have not been answered. GFM

[@chuckoaks6756]

If I have power to the valve and the tests show proper voltage on both pins could it be the valve its self? If so is there a way to check the valve mechanically? Do you have a video in this?

[@grayfurnaceman]

I there is 24v power to the valve, the valve has failed. The valves are not repairable. Also be sure gas is available to the valve. Hope this helps. GFM

[@chuckoaks6756]

turns out that the sensor on the pilot light had carbon on it and couldn't sense the pilot flame so it would shut down. I had a new sensor put in and it works perfect. I had checked every sensor but didn't realize that the pilot had one in it too.

[@mackscroggins9666]

Im getting a constant 14 volts to my gas valve. Once the hsi heats up the voltage drops to 11 volts then goes back to 14 volts. The gas valve is wired straight to the board with nothing in Series so Im assuming the board is bad. Any thoughts?

[@grayfurnaceman]

The 14 volts is a ghost voltage. Nothing there. You need symptoms. Inducer comes on? error code lights? GFM

[@mackscroggins9666]

Yes inducer came on replaced board and now unit is working properly

[@grayfurnaceman]

Merry Christmas GFM

[@flowc3598]

trying this with a furnace that has an electric ignitor unit.... once it starts making sparks the Voltmeter starts flashing all sorts of numbers. Like interference, how can I test?

[@grayfurnaceman]

I can't say I have ever seen that happen. GFM

[@deopadrequilaga4590]

Can you give me advice, i call the HVAC to replace my furnace blower motor start smoothly run like it was ,the guy came upstairs said there is big problem the gas pressure valve they couldn't adjust the pressure they used the reading tool says 4.6 supposed to be 3.5 they told me is to high need to shot off the gas unsafe to operate might cause fire or explosion that is there explanation to me they put the Red tagged the guy said need replacement the whole furnace they estimation $ 8k - $ 10k .i told the guy i did not asked for checking the gas pressure it's been running like that since I bought the house .

[@grayfurnaceman]

First, I would be concerned if the furnace had run for an extended time with manifold pressure that much higher than factory recommendations. There could be heat exchanger damage that could mean furnace replacement if the furnace has been installed over 10 years. The manifold pressure is adjustable and I have never seen a gas pressure regulator on a gas furnace that was not adjustable. Perhaps he found the gas regulator was defective. If so, the gas valve could be replaced rather than the entire furnace. That does not mean I would recommend gas valve replacement if, upon inspection, I found damage to the heat exchanger. A second opinion may be useful here. GFM

[@deopadrequilaga4590]

My furnace is 28years old ,i notice that day i have no hot water the next day the HVAC guy call me they forgot to turn back the water heater on .can you imagine if they forgot to call me ,I might to call the plumber that day that another expenses, They said they put redtagged I checked my furnace I can't find the redtagged i turn on my furnace is winter in canada I've been spending time observing my furnace in the basement ran fine. BIG THANK YOU FOR YOUR ADVICE

[@Kaibil66]

You're the best....master

[@enzoamore9173]

What's the natural gas pressure for a brand new gas valve set at brand new out of box?

[@electriccar3253]

It will certainly depend on the valve application but most are set to 3.5 in wc. It should be marked on the valve. GFM

[@scientist100]

When I plug the wires to the gas valve, the voltage does not show up as it would for the 5 seconds if it was unplugged (usually 28). Mine is just a 2 wire valve. I do notice that there is a spike and then goes back to zero very quickly, is it possible that there is an issue with the valve? My ghost voltage is 15 when it is unplugged. I have seen people test power with the valve plugged and they usually have the 28vac for the 5 seconds. Thank you for any help.

[@grayfurnaceman]

If you have a spike, the control boards has probably failed. You can double check by jumping power straight to the valve. If it opens, you have confirmed board failure. GFM

[@scientist100]

@@grayfurnaceman thank you for the feedback. Is it normal to show 28 volts when it is not plugged to the valve for the 5 seconds? 28 volts show as well when I manually turn off the valve with the power slider. It appears that the valve is bringing the voltage down for some reason. This is the only reason I suspect board, in an electrical system, wiring or transistors give up when the system is loaded and tests ok when not loaded.

[@grayfurnaceman]

@@scientist100 Open circuit voltage is always higher. When it loads, it should drop to 24-26V GFM

[@scientist100]

@@grayfurnaceman thank you for your reply. In my case reading 0 volts when it should read 24 indicates a problem with overload due to a malfunctioning valve or would it just be the board? My scenario doesnt male sense based on an open, I believe there is no open in the valve as it reads less than a mega ohm from either side so there is some sort of continuity.

[@grayfurnaceman]

@@scientist100 You need to know that these valves are DC. The valve has a built in rectifier that pretty much defeats ohm readings. In most cases, board failure is the culprit. GFM

[@igloo98]

I have studied your videos and have learned a lot. Nowhere on youtube have I seen a demonstration for the failure I am experiencing. The sequence of events seems normal. The inducer fan starts~the vacuum valve operates~the hot surface igniter heats up nicely~the gas valve opens with a little shutter and then for a very brief moment all jets fire with a nice blue flame then immediately they loose pressure and continue with a yellow stream of flame that does reach into the heat exchanger. I have cleaned the flame sensor which had carbon on it and that now allows the yellow flame to persist for 3 minutes or so before shutting down. It will continue to restart and repeat as the sequence starts over. I suspect the gas valve has failed. After watching this video, I will get back up there and check for voltage. And when it shuts down a couple jets stay lit for a minute or two with a small pilot like flame and then slowly die. And I have replaced the regulator at the propane tank. And the old one tested out fine too. Thanks for all you do on youtube!

[@grayfurnaceman]

Stuart Morse Even tho you have replaced the regulator, it sounds like a gas pressure problem. Are you sure you have enough propane? GFM

[@igloo98]

grayfurnaceman Just had a delivery of 40 gals in a 120 gal tank. Temperature outside is +25 night and +55 daytime. The Gas water heater is working just fine. Checked the voltage to the gas valve, 26v. Getting a 12v reading before the valve opens. The old regulator tested out at 14psi. I didn't test the new one. I wondered if the valve could be closing down. Probably not. If it opens at first it should stay open I would think.

[@modsquad67]

Gary, thanks for the videos. I really enjoy watching them. I'm having a problem with an Amana gas pack. The furnace won't fire. It has a Gemini 2 stage gas valve. I checked incoming pressure and I have 8" of w.c. When I cycle the heat I can feel the valve click like its opening but I'm not getting any pressure on the outlet side of the valve. I checked the voltage and I'm getting 24 volts to the high side but negative to the low side. I think that I correct. These Amanas are the same as a Goodman. They fire on high first them drop down to low after a minute and a half.

[@grayfurnaceman]

+modsquad67 My thought here is the gas valve has failed. GFM

[@modsquad67]

+grayfurnaceman my thoughts also. So I replaced it today and it's doing the same thing.

[@modsquad67]

+grayfurnaceman the home also has gas logs, and a gas water heater. They are working. I checked the flames on the gas logs and they looked good.

[@grayfurnaceman]

+modsquad67 Do you hear gas coming thru when there is a trial for ignition? GFM

[@modsquad67]

+grayfurnaceman no. I don't hear or smell any gas. The unit cycles like it should. I'm going to try and call the manufacturer today and verify the sequence of operation. The only other thing I think could be causing it is a partial blockage in the gas line. I'm getting 8" w.c. at the inlet of the valve but when I break the line open at the Union and open the valve the gas doesn't seem like it's really blowing out very hard. I know it's a 1/2 pound system. That may be throwing me off. Thanks for your help. Your videos make me a better service tech. I have learned so much from watching your videos.

[@deanmartin1966]

Great video thanks for sharing

[@ChicagoCactusKing]

Hey, I have a similar gas valve but the medium heat and high heat are jumped out? Is that just a way to use a two stage gas valve for single stage heating? Thanks

[@grayfurnaceman]

Unless your furnace is a 2 stage, the 2 solenoids on the valve are redundant valves. GFM

[@inquisitvem6723]

that light switch next to your furnace. does that need to be turned off before testing the wires?

[@grayfurnaceman]

No, you are checking for voltage, so you need power to the furnace. You also must have the thermostat calling for heat. GFM

[@theoldman443]

Lennox 21 plus... when I run a volt test I got 12 volts. What would cause that?

[@grayfurnaceman]

That's a ghost voltage. There is no power to the valve. GFM

[@ramcharge68]

I have a temp star when it first start up it lights and run for about 2 or 3 minutes and then flame goes out and it relights but now it runs about 10 seconds so I changed the ignitor spark & pilot burner and it does the same thing,it has a intermittent on it also,what could be the problem?

[@grayfurnaceman]

First, is your furnace vented with plastic pipe? If so you may have a blockage in the vent or combustion air. GFM

[@ramcharge68]

Its vented with metal,but a new coil was installed during the summer

[@grayfurnaceman]

I would be looking for vent pressure problems. Possible inducer not producing enough vacuum. Pressure switch tubing blockages. You could also have a crack in the heat exchanger. Look for flame rollout of the burners. GFM

[@ramcharge68]

OK I will look in the morning. Thank you for your help grayfurnaceman

[@ramcharge68]

THANKS FOR YOUR HELP GRAYFURNACEMAN I CHECKED TODAY AND THE FLAME WAS ROLLING OUT AND IT GAVE OUT A SOUND ON START UP WHEN IT LIGHTS THE BURNERS AS IF GAS HAD BUILT UP(POOF) SO I AM CONDEMNING THIS FURNACE.

[@andrewnichols1240]

My Amana was working fine but gas company forgot to turn my meter to house valve on after installing a new meter. ?my gas bill says I using 8 therms per month before I turned my valve on?

[@griffinlandis9337]

I have the second valve that you show in the video with only 2 prongs. When I start it up, the inducer starts, the igniter glows but no flame and I hear no gas. I read 19v to the gas valve. Is this from a bad board?

[@donaldlee6760]

Hello Griffin, was 19v due to a bad board?

[@justdissin7340]

I got numbers from 1-5 on my gas valve which ones does the leads go on?

[@grayfurnaceman]

I will need the model number of the valve. GFM

[@smarterworkout]

I got 27.7 is this good or normal?

[@grayfurnaceman]

Looks normal. GFM

[@henryodogwu6604]

what would be the problem if 24v is registered when wires are unplugged from the gas valve, but the voltage drops when wires are connected to the gas valve?

[@grayfurnaceman]

Probably a bad control board. There is no real power there, just a ghost voltage. GFM

[@IamFreeRu]

I ran the test with volt meter. I️ am not getting power to the gas valve. So i have to replace the main board? That’s the solution or something else.

[@camphopper9468]

what about high on gas valve please explain we know there's voltage to the low but what about the high when does the high kick in

[@grayfurnaceman]

Probably the best way to explain this is to refer you to a video that shows ho the 2d stage is activated: kzbin.info/www/bejne/l3PMZJJ_jbd2msk Hope it helps. GFM

[@jimervin387]

If the gas valve is warm with the thermostat on, that should be enough to tell you that voltage is getting to it, shouldn't it? I have a 1983

[@grayfurnaceman]

No. You need to check voltage at the valve. GFM

[@jimervin387]

Okay I've done that. I'm not sure if I'm using my voltmeter correctly but I read 130 on the AC line with the thermostat turned up a little. If I have a bad gas valve, though, shouldn't I consider replacing the furnace since it's a 1983 model Lennox?

[@grayfurnaceman]

First, you should read 24 volts at the gas valve terminals.. Yes, it should be replaced if there is a major failure. Do not throw good money after bad. GFM

[@jimervin387]

Thanks. I"ve been quoted a price of around five hundred bucks to have a contractor come and replace the gas valve. So it's looks like I could be throwing good money after bad, especially if I have another problem later. I've already replaced the thermocoupler tube last November. At least it's summer now.

[@andrewthacker114]

Thanks good clip

[@fullofbullets58]

hello... I have a furnace that is not operating. i went through the sequence of operation and i am stopped at the gas valve. the furnace is an older keeprite with a spark ignition attached to the separate tube for the pilot control. The ignitor sparks, and the pilot valve releases a small puff of gas, which ignites then almost instantly goes out. There is no thermocouple, there appears to have no pilot proving sensor. The main in the gas valve isn't opening and releasing gas.. i am perplexed... WHAT do i do? please help me

[@grayfurnaceman]

Richard Gibson This one sounds like a Honeywell Smart valve. Take a look at this one: kzbin.info/www/bejne/hF6QdICPjderhtU GFM

[@fullofbullets58]

i believe the issue is in the spark ignitor.. What i don't understand is how is the spark ignitor stick is also the sensor? The ignitor is attached to the pilot tubing. It is fed into the module under SPARK. there are no other wires or devices going to the ignitor. Only one high tension wire that goes from ignitor to the spark connection on the module. should there be a separate device or wire to prove the pilot flame? or is it all done through the wire/rod(spark)?? i tried to clean it and it didnt work

[@JoseNevarez]

What if I’m not receiving any voltage to my gas valve

[@grayfurnaceman]

If you are not getting power to the gas valve during a trial for ignition, you probably a safety shutdown of some component during the trial. Pressure switch, limit open, etc. GFM

[@jaiho5857]

What’s the MP or PM

[@hireme3864]

Is it AC or DC ? If this comes directly from transfermer then it is DC for sure, but looks like it is coming from Circuit board

[@grayfurnaceman]

It is AC. The transformer is also AC. The power is rectified inside the gas valve. GFM

[@JohnDoe-zl9si]

i get voltage at gas valve have glow on igniter but furnace won't ignite, i believe valve is bad, but can smell gas after the furnace attempts to ignite.is that normal with a bad valve?

[@grayfurnaceman]

No. This one could be dirty burners, ignitor not getting hot enough( most ignitors that are above 150 ohms are suspect), or possibly a crack in the heat exchanger. Hope this helps. GFM

[@jimclark9077]

Thank you for the video. I have an intermittent problem. Sometimes the furnace will start normally, voltage is fine to the gas valve. Sometimes surface igniter comes on and there is no voltage at the gas valve, it cycles through again and starts properly. Never any error codes and it never takes more than 2 attempts to start. Thoughts?

[@grayfurnaceman]

This could be either a failure of the control board, or an intermittent open in the plug that connects the gas valve to the control board. Try moving the plug around when there is a failure. GFM

[@edmarsh1965]

good job,thanks for video.

[@grayfurnaceman]

Welcome GFM

[@jeffreyplumber1975]

In regard to the gas pipe union inside the furnace> I know gas flex isnt allowed in my area. I sure dont like a union in there perhaps a right left nipple and coupling. Im uncertain as to legality as you said gfm It might not be concield. But that union looked questionable to me. BTW thanks for your help GFM

[@andrewnichols1240]

Is there a valve on the gas entrance meter

[@grayfurnaceman]

There is a valve on the gas valve and also one field installed on the gas line close to the appliance. GFM

[@compton22101]

I'm getting a voltage reading of only 12.7 whats that mean?

[@jeffmattero8500]

I am a novice, but I would suggest testing at the transformer to see if it is putting out 24 - 28 volts there. If not, I would replace the transformer. Again, I am only answering this as a novice. I have had this same problem in the past, and that is what I did, and it worked.

[@compton22101]

Jeff Mattero thank you Jeff. Got it figured out it just needed to be reset.

[@bluwng]

Mine functions but it buzzes like a mini chainsaw. Only getting 12v.

[@melissasundstrom2075]

Hello, love your videos!! I have an older '87 Kenmore condensing furnace mode#867769224. I've owned my home since '94, furnace has no other issues, works great. Not too many issues in the past, blower motor and limit switch in 2009 and 2010. Now fins going bad on blower wheel and I might have to replace motor again, it's been 8 years, but service tech had limit switch at 60 90 220. It s/b 90 135 180. My question, gas valve vr8440p2088 has a slight gas odor in the last 6 months since the squirrel cage is humming and now it's real loud and part on order for it. I'm having issues with replacement of gas valve. Is it normal to have a slight gas smell? Also notice the limit switch bounces before it shuts off at 180. Seems like it cycles down before the thermostat is satisfied, but I don't keep my house very warm, 68-69 degrees. Of course motor comes on within a couple minutes or less after thermostat calls for heat. At least now, my blower turns off with the adjustments of limit switch...thanks to your videos!! Thanks again for all you've done!!

[@grayfurnaceman]

Melissa Wery The gas valve should have no gas odor. If the smell is determined to be from the valve, replace it. If from the piping, repair the leak. GFM

[@melissasundstrom2075]

Valve, wheel, blower and limit fan switch parts came in. Waiting for service tech next week to install. Now it's short cycling, blower wheel isn't very loud now. I cleaned out the drain attached to the flue plastic pipe. Now I'm noticing water in the tubes attached to neutralize tubing. I'm wondering if it short cycles, because of blower motor getting weak or I have a air flow issue.

[@grayfurnaceman]

Probably air flow. GFM

[@steelersgnome]

I get approx. 26 volts constantly to the valve and this drops only when I turn the thermostat below room temperature. The furnace still doesn't light. Is this a gas valve problem or something else, or both?

[@grayfurnaceman]

If you have power to the valve, either the gas valve has failed or there is no gas supply. GFM

[@frontiermarvin71]

Thank you for sharing your information

[@dwdrumwiz]

Try UNIONS and BUSHINGS in concealed locations and see what qualifies as a Concealed location.

[@grayfurnaceman]

Just so we are clear, a concealed location is: A location that cannot be accessed without damaging permanent parts of the building structure or finish surface. Spaces above, below or behind readily removable panels or doors shall not be considered concealed. I think what they trying to avoid is placing a union in a space that cannot be reached from both sides to be tightened. GFM

[@bills6946]

The worse thing a tech can do is leave a furnace in service if he tapped the valve at voltage to get it to open. Yes he got heat for the customer until he can get a new valve, but if the valve can get stuck closed, it can get stuck opened and cause a catastrophic explosion. Never leave an intermittent valve in service.

[@theoldman443]

Yes it starts

[@grayfurnaceman]

If the inducer starts, check for power to the control board. If there is power in, and no power out to the gas valve, the board has failed. GFM

[@joseportillo4255]

I have a problem with the gas valve, the pilot is on when the temperature in thermostat is increase the flame come on, it heat the house when the thermostat is satisfied the flame is shutdown but 30/45 second later the pilot goes off, this particular valve is brand new is a Honeywell type 400/24 volts.. does any body has a comments I have had three difference plumber with not solution.

[@grayfurnaceman]

You need to look at the pilot. Is it covering the thermocouple completely? Is it blue? Yellow means dirty pilot. GFM

[@shelby50411]

Good video...my issue is no gas....when i do this voltage check i only get about 18v for less than 1 second.....then goes to zero....

[@grayfurnaceman]

On a trial for ignition, the gas valve should read 24 to 29 volts for from 4 to 7 seconds. If it immediately goes to zero, I would be looking at either a loose wire or a control board failure. GFM

[@bonafide6464]

lennox 80uhg4/5-100a-3 is the full product number of my previous comment. See below.

[@rivernet62]

Quality tested WITH PRIDE by Carole Lynn K in Trenton NJ

[@ryk1265]

Check!

[@williammorgan9626]

Ñ

[@islamerica3032]

Love the vids...hate the teeth sucking.

[@qonib]

After HVAC technician charged me $389 for a gas valve that cost only $120 I felt scammed.

[@terrytuepah171]

After I went to a lawyer’s office and got a letter he charged me a $189 I felt scammed. Same thing. Your not paying them for what they do your paying them for what they know.

[@qonib]

@@terrytuepah171 so charging you 3 times the cost of the part means what they know?????

[@tinoaguilar7042]

Sure does if he fixed it lol

[@tylerskjonsby3263]

@@qonib yup. Learn to fix it yourself or pay someone that has years of experience and training to fix it for you.

[@qonib]

@@tylerskjonsby3263 I'm not talking about labor cost!! what I'm saying is he charged me $389 for a part that's $120. so isn't that a scam?