Fixing This Furnace Was A Learning Experience!

[@hvacsteve2o9]

One of my techs called me today, saying he knows the gas valve is bad because he’s getting 24V but no outlet pressure. I told him, before replacing the valve, to grab a 24V relay to see if it pulls in-it could be phantom voltage from the control board. He told me I was crazy. Guess what? It was a bad board. The gas valve was fine, and the relay didn’t pull in.

[@bills6946]

When measuring voltage at a valve, I disconnect the wires and put the leads on the wires. If the valve coil is shorted, it will pull the voltage down and you could be fooled into thinking you have a bad board.

[@TheBdog2009]

Crap I knew someone would beat me to saying this.. 😅 I'm not a parrot! 😊

[@russelldenton8753]

can you explain this in more detail please? I want to understand this more thoroughly.

[@catfishking7274]

I’ve found it best to test both with wires on valve and off because sometimes if the board is bad it will give 24 volts out but when u put it on the valve it will disappear I usually jump out the gas valve straight to 24 V while using a manometer and that will tell if valve is definitely bad

[@mcleodautomation]

@russelldenton8753 The reason for removing the leads when ohming out a device, such as contacts on a control board, is to ensure you get an accurate and reliable measurement. If the leads are not disconnected, the meter might pick up resistance from parallel paths in the circuit, meaning it could measure additional components or wiring that are still connected. This will result in an inaccurate reading that doesn’t reflect the true resistance of the device you’re testing. Additionally, backfeeding can occur when there is residual voltage or current present in the circuit. This can interfere with the measurement and may even damage the meter if it’s not designed to handle it. For example, when you ohm out contacts on a control board without disconnecting the leads, the reading is often not zero. This happens because the meter is measuring resistance not just through the contacts but also through other parts of the circuit, such as resistors or capacitors that may still be connected. Disconnecting the leads ensures the device is isolated.

[@edwindavitian2322]

You were lucky that gas valve was not crack. You tightened tomuch.😊

[@josephbermudez8073]

I learned from my senior guy not to measure at the valve but disconnect the wires one confirm 24 from the board if not 24 bad board if there is 24 volts take a contactor and see if it pulls the contactor in if it closes it bad valve.

[@greglowery65]

that "i think i can get one more turn on this" always gets you lol

[@jthonn]

Gas pipe does not have to be super tight

[@melundank1039]

@@jthonn especially the 3.5 side with open orifices

[@teeknowstech]

Man i love watching his videos he breaks everything down and shows how he fix everything which is awesome most other youtubers don't show ever step this guy really know how to make a video brother keep doing what u doing man u rock

[@HVACGUY]

Thanks

[@deanmartin1966]

I knew as soon as the video started what the problem was. Why? Because I had the same problem. I was checking for 24 V while the leads were connected to the bad gas valve. For some reason that bad coil wouldn’t let the voltage go through. I would get 9 V at one point. Then I’d get 0 V. I learned to test for 24 V without the leads connected. Good video man. By the way, the green ground wire that was loose on the inducer motor we usually attached to the extra ground terminals on the gas valve. I really don’t think it matters to be honest.

[@yz250a]

Curtis, take it easy on torquing that gas valve, you could split it or distort the housing. It's only 5" W.C.

[@svdea]

I have had that problem. if you took the wires off the gas valve and tested for you 24v you would see it doesn't drop out. when you test for 24v with the wires on it it will drop out.

[@russelldenton8753]

what do you mean by voltage dropping out?

[@Alan-jx7uk]

@@russelldenton8753 Dropping out = the 24v will to away.

[@kirn.creations]

1st Verify control voltage on the isolated wires. 2nd install wires back on valve and take a amp draw to check the coil. It’s usually spot on with the name plate. Great content, love your videos!

[@DonTgurdy1488]

Also, your meter averages the voltage. If you ever run into this issue, or one similar to it, bypass the vacuum switch and see if that is the issue. If a vacuum switch is failing and is opening and closing to quickly, your volt meter wont see it and it will still show a steady 24 volts going to the valve. I know that you solved this issue, just throwing it out there. One time i was working on a furnace and thought i was getting a steady 24 volts at the gas valve. I replaced the valve. Same issue. I replaced the valve again. Same issue. I bypassed the vacuum switch and it was what was causing the gas valve to open and close rapidly.

[@everettstevenson2111]

again it is all about timing and safety. Natural gas is no kind of play toy, it has killed people in the pass.

[@catfishking7274]

I find it best to jump gas valve out to 24v while using a manometer any time I think it might be a bad gas valve or board it takes all the guess work out. u could have probably diagnosed this unit in 10 minutes by doing so. But keep up the good work brother I love the videos

[@denverbraughler3948]

Correct answer ⤴

[@kens.3729]

Getting Stumped is Not in your Vocabulary. Great job, Curtis. 👍🙏

[@helmsajr]

Had the same problem before Curtis. Great job.

[@HVACGUY]

Thanks 👍

[@lesliecook9760]

I use a 24 volt contactor to check if the voltage is dropping out

[@yrs94]

Genius

[@30rdmaga]

That's a great idea 💡

[@popradcan]

👍

[@stevencossaboon3237]

Great job Curtis, that one was a head scratcher.

[@jthonn]

Main thing is you figured it out. Nice work

[@wmcomprev]

I'll start with, I hate intermittent. An intermittent open in the valve's windings would have caused the gas to turn off, but left you with 24v at the contacts. However, an intermittent short in the windings would also cause the gas to go off, but leave you with 0v at the contacts. So, it appears this valve had in intermittent internal short.

[@denverbraughler3948]

What you could have done is to power the valve directly from a transformer to see whether it would open. When the gas is on, you can verify the pressure using the test port on the valve. If the valve doesn’t open with 24V, it’s defective. The slow open circuitry is built into the valve. That’s why you see megohm resistance, not a coil.

[@co5863]

He does not know everything like u.

[@ronroberts7566]

Good call on separation of the grounds from common, flame rectification circuit can be finicky when unit not grounded correctly

[@LeoLoder]

Might I suggest that when tighting the gas valve to the manifold that's fine, but always try to put a nipple in the in port of the valve. This will prevent distortion of the threads on the valve. It doesn't happen much but better safe than sorry. Nice video!

[@AaronPowellvox]

The coil in the valve is shorted to ground causing the board to reset when 24v is applied.

[@KnightT60]

I’m not an HVAC tech and have no explanation for why they’re manufactured like this, but I’ll bet the valve has a DC coil and contains an internal diode. I imagine if you check one using an old analog ohm meter or a meter with a diode test function you’ll get wildly different readings. There’s no way the coil resistance can be anywhere near the megohm region and work. Maybe a few thousand ohms tops.

[@everettstevenson2111]

it is all about timing and safety, and system will lock itself out.

[@frednepa9690]

Always like your videos. You always show the good and bad. It's appreciated.

[@cozccs]

Great work chasing down diagnose of bad valve. The only other thing I would have checked is incoming gas pressure , and no pressure switch restrictions.

[@bobboscarato1313]

Well its working fine; there may be a few more customers wanting to get their heaters repaired as well.-

[@johnwalker890]

Good job Curtis.........

[@curt3548]

Did you get a diagnostic code upon failure to ignite? I would be checking pressure switch for make pressure. also, you can get a false 24v that doesn't hold under a load. one way to check this is to remove gas valve wires and attach them to a contactor coil to see if it holds the contactor in. could be a lot of things. dirty orifice, dirty burners. check manifold pressure in and out of the gas valve while fired. a circuit board and a gas valve replacements are half the cost of replacing that furnace.

[@everettstevenson2111]

it is all about timing and safety,

[@boby115]

Just so you know the gas line should have a sediment trap (drip leg ) before the gas valve & the flex connector should not enter cabinet of the furnace. NFPA 54 requirements but it is what it is & you got them going 👍.

[@DennisDuffy-n8g]

I just had a similar issue today on a ducane furnace ended up being the gas valve as well unbelievable huh 😂

[@stephenbullock-yn3vh]

Excellent work curtis 👍

[@HVACGUY]

Thanks 👍

[@franks6837]

Channel lock tight tgen make sure it's pointed where you want to to and that's it . The new valves are crap and easy to crack. It'll never leak I promise

[@Vinmaster73]

Glad they'll be nice and warm. Tis chilly outside. We're kinda cold here in Minnesota -1 heading for -30 wind chill. So having the furnaces checked out in fall is a must do! Great job! And please keep the videos coming! You've helped this homeowner save some $ especially your AC postings re: capacitors replacement and coil cleaning. Merry Christmas from Minnesota!

[@JimGnatek-y7z]

The board most likely has to see a certain amount of resistance in the gas valve. That's why when you put your volt meter on it you created enough resistance and the valve turned on but went off as soon as you removed your leads. Way over tightening on the valve especially using the opposite end to tighten. You can oval out that end causing a leak and then you bought a nice paper weight for your desk.

[@robalexander7348]

Well done Curtis, you rectified that job nicely, and it runs well now.. BTW,, Ted has a video to view 😮 Au

[@rgmatta3524]

Interesting find. Good troubleshooting skills.

[@HVACGUY]

Thanks

[@TomLawson05]

Great job Curtis thanks for the video

[@HVACGUY]

You bet

[@30rdmaga]

Well done 👍

[@HVACGUY]

Thank you 👍

[@danparisi1587]

Had the same problem on the same furnace replaced the board twice before figuring out it was the valve. Mine would would fire every time for a second then drop out like a flame sensor. Once I took the wires off the valve to test 24v power stayed there longer . That won't ever get me again

[@bobboscarato1313]

Well until the next time when they redesign the gas valve. lol

[@horsth9566]

Having 24 volts at the valve is not conclusive! Checking the current going thru the valve however is. Checking the resistance (ohm) of the valve is not conclusive either, because there is a bridge rectifier within the circuit. The on-off switch can be faulty. They are very flimsy but easy to fix once the cover is removed.

[@TheBdog2009]

Im sure you knew this already. You just forget. All the cooling calls in the summer and rarely do gas valves fail that often. It happens brother just try to remember the next heating season or whenever you have an issue like this one again.

[@michelgrenier1878]

A tricky one , Most of us would have blamed the flame sensor . But it likely was sending 7 micro amps ?

[@allanford1582]

Rheem mid limit in fan compartment in series with gas valve, you will get ignitor but no power to gas valve has fooled me once lol

[@HVACGUY]

That wasn’t the problem

[@30rdmaga]

Same here

[@zproxiimiity7733]

I ALWAYS ISOLATE

[@scottharbaugh431]

Can’t check ohms in gas valve has a diode bridge

[@wallywal5475]

Wished they made it easier. Maybe a torque spec would confirming.

[@OldguyinBelize]

i'm an old,, very old combustion tech, and i enjoy trying to beat you to the problem. in this case i was heading to the igniter not proving. good job! proving me wrong! plus,, dude,, why don't you use aluminum pipe wrenches!

[@HVACGUY]

Sentimental reasons. I’ve had the same pipe wrenches for over 20 years

[@tedhicks5431]

I had one similar ended up being vac switch couldn't handle load anyway when it started up i bypass vac unit run fine pulled jumper office would drop out replaced switch heat on

[@30rdmaga]

Veto pro pac and m12 driver 👍

[@Sctronic209]

There usually diodes in the valves.

[@john7017]

That's a counterflow Rheem furnace on its side, there is a low temp limit in the blower compartment that breaks power only to the gas valve and when it's failing you will get intermittent shut downs and power loss to the gas valve. It may be a call back.

[@HVACGUY]

I did check that.

[@bigd3104]

Is that just on Rheem? Thanks.

[@HVACGUY]

@@bigd3104I’ve only seen those limits that kill the valve on these furnaces

[@bigd3104]

@HVACGUY OK, Thanks!

[@bawgwon]

Dang valves!

[@bobboscarato1313]

How can HVAC people make money if nothing breaks down? lol

[@ivancook1247]

I always use a contacter in place of gas valve

[@andersonli9707]

i remember same problem happened to the steven

[@bamatractor]

I guess the board knew the gas valve was bad and shut it off. The first time I pulled a cover off a unit and seen three big huge control boards on a unit, thats when I decided I got to get out of this business.

[@everettstevenson2111]

Hey HVAC Guy not easy being cheesy. I like your podcast/social media, looking thru some comments???. I am old school myself, but when it come too those logic boards. It's all about timing and safety, some of those old logic boards do have an reset for it's lockout system. Again you are no mikey pipes plumbing trying to sell me on an tee shirt and coffee mug. Love you buddy, you be safe out there.

[@redneckways1617]

Could have saved yourself a lot of guesswork and doubting yourself if you would read the amp draw also on your low voltage…some control boards will reset ( just like thermostats) when they are pulling a higher than normal amp draw…

[@harrydickson4575]

👍👍👍

[@dogdiggingrj2089]

Watching you cranking down them pipes on that value i was waiting for that value to crack there only made of pot metal and i never use pipe dope on values, only Teflon tape to try to make sure pipe dope doesn't get in value

[@bills6946]

That isn’t pot metal. It is pure Chineseium alloy or Mexicanium alloy.

[@bobboscarato1313]

@@bills6946 Are those Registered trade brands? lol

[@bills6946]

@@bobboscarato1313Chineseium is derived from stolen research work at MIT by a Chinese National on an expired student visa. The alloy was developed by Professor Adolph Schnitzengruben and his graduate students 11 years ago. 5 years of research and development gone.

[@stevea6722]

@@bobboscarato1313 Probably not, but definitely accurate composition!

[@bills6946]

@@bobboscarato1313 It is a composite alloy of Bud Lite beer cans recycled by a Chinese smelter.

[@candudaddy]

Ya’ know, if manufacturers put som troubleshooting data in their product packaging this could have been a less troublesome repair. Maybe if they put in the booklet that the dc resistance across the terminals of the gas valve when new was ~7meg and that there should be infinite resistance from both terminals to ground then you could infer the coil was shorted to ground or to itself. Maybe a good practice would be to write a note in the cabinet when a component is replaced with that kind of info?

[@Mr572u]

Get you a Crescent wrench or two.

[@tedperry2441]

Check the ground on the board.

[@TedCookHVAC]

Hate it when I get stumped !!

[@jewellhirsch1694]

Hi Mr. mechanic I don’t know why you wouldn’t check with the wires off of the valve just to see if you could get established 24 V if you couldn’t get 24 V with the valve out of the circuit then you know for sure they’re over is the problem that have anything to do with any safeties or anything doing with the machine? That’s what I would check first then I have a note to go from there over for sure, but I think something is shorting after your your 24 causing it not to show up anyway that’s my little talk for today. This is Fred from Tallahassee.

[@jaceplayz1288]

It’s only cast aluminum don’t want to break it before you can install it. IJS🤷🏾‍♂️, great call though with the gas valve and not the control board. Ohms was the tell tell sign.

[@jimdavis6833]

69K and rising.

[@HVACingMyWay]

I hate those Honeywell valves they are horrible about sticking open and closed too.

[@HfJax]

Hey Curtis thanks for the video, what magnet are you using looks so handy, I could use one for the winter since we have many no heat calls

[@justinrichard4190]

Supco furnace pro clip. Amazon sells them

[@HfJax]

@@justinrichard4190 thank you

[@HVACGUY]

Left a link in description

[@nichols0497]

They work great I got one a month ago.

[@ssrrocks22]

Loose wires in your molex plug?

[@sergiohernandez4163]

Does sll gas valves ohms same readings? I didnt even know you could ohmed them out.

[@HVACGUY]

No they all aren’t the same

[@ellistravis]

Those intermittent shorts can be a head scratcher, I had a contactor coil with the same issue I replaced the control board and still had the same trouble , I ohm out the coil contactor it was up to spec but once I replaced it the system work perfectly😅

[@edwardlowery6510]

that’s what you check

[@edwardlowery6510]

put the pipe wrench on top

[@MrDookieDan]

How would you charge for that?

[@patricksmith8427]

What brand is your tool bag?

[@HVACGUY]

Veto tech pac mc

[@uzlonewolf]

23:15 "Veto Pro Pac"

[@edwardlowery6510]

you are testing for voltage or the valve

[@NancyVanegasHVAC]

I may be wrong but from the sequence of operation once the igniters receive the 120v from the board and gets to a certain temperature it sends voltage to the board witch then sends 24v to the gas valve 🤷‍♀️ but great job 👍🏽!!

[@everettstevenson2111]

again it is all about timing and safety. Natural gas is no kind of play toy. It has killed people before.

[@usahoangsatruongsa]

Hi Curtis when you trying to ohm out the gas valve that won't give much clue because the gas valve they used DC voltage not AC voltage. When you ohm it out you actually ohm out the dc rectified circuit in there.

[@edwardlowery6510]

it’s called heat

[@paullehman8652]

What’s that thing with the big wires connected to it behind your drivers seat

[@edwardlowery6510]

relay

[@julr3730]

why are you look younger maybe than your actual age? may i know how old r you?

[@edwardlowery6510]

you can’t get a reading when it’s conne

[@edwardlowery6510]

skip that

[@DeclanBirmingham]

first

[@donalddohrn8452]

Dam Curtis,, its low pressure gas,, you don;t have to monkey tight the dam thing...

[@donalddohrn8452]

Monkey fistet then......