How To Troubleshoot A Bad Control Board! Fan Wont Come On

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In this video we walk you through how to diagnose or troubleshoot a bad control board. This same technique applies for A/C as well if your fan isnt running, you'd jump R and Y instead of R and W. Then you'd check for voltage between the neutral pin and COOL instead of Heat. I hope you found this video informative! If so make sure and leave it a like and subscribe to our channel!
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[@tensecondbuickgn]

As a retired ASE master automotive tech, these videos are fantastic to watch. Very clear and precise and dumbed down enough for the average Joe

[@YouTube_T45K]

My thoughts exactly

[@Hxneybee395]

Had a customer short a board on an inverter system watching one of these videos. Keep cranking them out!

[@henryayala9657]

Thanks for all your videos. I had the same unit with the same problem. The root cause was a cold solder joint on a white terminal connector. This was caused by the weight of the wires and an unbalanced blower. Having the control board mounted to the blower housing is probably not the best design but the stock wires did not allow relocating for me.

[@nvatlanticcity3]

Great tip on testing the blower by connecting it to the transformer near the door. Thank you for your easy to follow video.

[@diyhvacguy]

Yea! Definitely using that truck next time I’m diagnosing a furnace with no blower!

[@borshardsd]

Lolol was it the transformer or the DOOR SWITCH. who knows good luck ;)

[@BeersHVAC]

Great tip on sending 120V directly to the blower speed tap! I will be using that one!

[@bawipengcin8591]

Thank you for the tips , Man. I was able to diagnose for Bad board by your knowledge sharing. Please keep up sharing you knowledge

[@diyhvacguy]

Awesome . Glad to hear it

[@andresbarragan8595]

FROM CHICAGO IM YOUR #1 FOLOWING YOUR VIDEOS THANK YOU SO MUCH

[@lego40404]

I got a emergency service call this morning with identical issue on a Emerson, only difference was I had zero volts at heat stake on tab. I know those black box relays on the boards can stick as they get older so I did the tapping on them to see if I can free them up for now till I get a replacement. Nope. Being the weekend and the burbs of Buffalo, I needed a work around, hmm. My board has a tab just for constant fan run, (like you would set your thermostat to fan always on and circulating the air)that let me run unit without it tripping on thermal overload. It’s a temp fix so heat does operate properly and furnace shuts off when setpoint is met. Love your videos. I can’t remember if your the guy who did the video on the kiawets dmm amprobe but I’m glad I picked one up

[@jaykeller1]

great quick test for jumping out the blower thank you sir!

[@ReverendRichie]

Thank you for your excellent videos; the above video makes total sense and is the source of my problem. Interestingly, the blower motor comes on when a call for FAN or Cooling is received but not for a Call for heat. It APPEARS that the call for heat and the call for the FAN to energize are two separate circuits. I ASSUME is for the blower to run at a lower rate during the demand for heat. I need to verify this, but it is the only thing that makes sense. Thanks for the simple motor test; that should help me immensely.

[@JP-mk3bb]

@The DIY HVAC Guy, firstly thank you for taking the time to film such clear and professional videos. I'm having this exact issue after following the instructions it seems as though my control board is bad. I have a lennox 80mgf3 60a-12 and have a surelight model # 50A62-121 control board. I've found one that says it's compatible but it's model # 50A66-123-01. Can you please let me know if that would work with my unit? Any help would be greatly appreciated. Thanks again!

[@chrisgreen177]

I'm an electronics troubleshooter and repairer by training. I was told that the control board was bad on my parents furnace and had to be replaced by a local HVAC service company. It was winter here in Wisconsin, so I paid $2700 to have the board replaced, because I didn't know how long it would take me to get around to troubleshooting the "bad board", replacing components and repairing it, but, I did request to keep the bad board after they replace it with new one. I was told that they did not leave bad components with the customer, and would not let me keep it. That made me very suspicious. For all I know, it could have been something as minor as a series of resistors, a relay, a capacitors, a cold solder joint, or some other components that very rudimentary board had that was degraded, shorted or open. I just found that very suspect, especially with him trying to charge $290 to replace a flame sensor that was only reading .30 ohms out of the +/- window tolerance. He didn't even offer to clean it for me.

[@diyhvacguy]

Sounds like you need to find a small family owned hvac business that’s trustworthy!

[@hafeezurrahman1000]

Thanks for sharing your story.

[@Nine_883]

People do not generally repair these board, but if you have the skills then by al means. The being said a typical universal board will run the contractor between $100-$200 and takes less than an hour to replace. Maybe even 20 minutes depending on the board and accessibility. So even if he did it on Christmas Night Holiday rates and it took an hour he got you for at least $2000. The boards are pretty much plug and play with a few minor modifications (such as cutting jumpers) on a Universal type. That guy should be in prison.

[@chrisgreen177]

@@Nine_883 I was pretty disgusted with the cost. They have people at their mercy, especially during the winter. All this was after he tried every sales pitch in the book to get me to finance a replacement 90% efficiency furnace installed for $5800.

[@ajahijernigan4051]

@@Nine_883 agreed I don’t know anyone who repairs but that’s a lot of money but I will say due to circumstances idk how much they had to pay a guy to leave his family to do this

[@marcosylvia5704]

Awesome video. You make it look so easy. Thank you.

[@fernandofrancisco3106]

Great video very informative thank you

[@paull2089]

Thanks for showing us your trouble shooting skills

[@billmcmaster7909]

Some good information that I'll use down the road.

[@ohiopat]

I bet if you pulled the yellow wire half off so that you could read the voltage with it hooked up it would have been 0. There are a lot of transient "ghost" voltages on circuit boards due to the nature of electronics.

[@diyhvacguy]

I did that and it still said 115. I didn’t show it but I replaced the blower motor because of that. Only to find that it did the same problem. The board was the fix for this one. That video comes out in a few days.

[@byronsinclair3956]

Great videos. I’m watching as much as I can. Gonna try and tackle new heat pump upgrade after watching many of your videos. Just trying to get through the summer heat before attempting it this fall. I know this pertains to the furnace/heat but could the same procedure/test be done to verify if the board bad if the blower motor unexpectedly cuts off/wont start when thermostat is calling for cooling? Basically instead of testing the heat pin (yellow/heat) and neutral, could you do the same voltage check for the cooling pin and neutral? The capacitor and blower motor are new (wish I had found this video a couple days ago). Freon flows, no obstructions/new filter, compressor functions. Fan stops less than a minute after stat calls for cooling. I’m wondering if it’s a faulty board and if this would be a good way to determine that.

[@gotchaplumber]

Great tip!

[@georgekern6528]

Great video! Well done! Cheers! George

[@diyhvacguy]

Thank you sir!

[@1255You]

Hey HVAC Guy, you have really excellent videos & I've learned a lot watching them. This is off topic for this particular video but I was hoping you could do a video on identifying the proper capacitor to use on the condenser side of the system. The original on mine has no identifiable markings I can use to obtain a replacement due to corrosion on it. Or perhaps you can just push me in the right direction to a video you may have already done on this issue. Many thanks in advance.

[@diyhvacguy]

Great idea! Until I make that video, if you’re trying to find the right capacitor right now, you can punch in the actual condenser model or serial number in repairclinic.com and it will give you a parts list for that particular unit. Or if your capacitor is still good and your system is running, you can use a multi meter to check the existing one, and then purchase a replacement. Hope this help! Cheers

[@adolfovazquez8427]

Great video thanks for sharing you are the best another tip for my book

[@Jaylenn.]

Couldn’t you just jumper R and G to trouble shoot it ?

[@jollyscaria1922]

Pcb bord power checking trsding trsformd low volt rc rg comon cool and checking r using strge comrinv anx checking ry 24v rg ond ny fsn low high meom oin power met checkinvg

[@binnsbrian]

Great information. One problem i find is I went to a heating and air conditioning supply and they wouldn't sell me parts because I didn't has a licence.

[@diyhvacguy]

Yes that is a very common problem. A lot of times the parts can be found at repairclinic.com but you’ll have to wait a few days. Next time, send me a message at [e-mail] and I’ll see if I can call in a part and you can go pick it up 🤘🏼

[@binnsbrian]

@@diyhvacguy Thanks

[@mauriciomachado5227]

Great video and I learn a lot from them, so thank you. When the Red LED is blinking on the control board, does that mean the board is bad or does it blink all the time?

[@WildChildRecovery]

Some boards will have a blink pattern to specify a fault code. Usually the patterns are labeled on the cover or in a manual.

[@aftrwhlcrocs]

Thanks!

[@user-gd5bn2qp2c]

Really like the trick to test the fan motor from the switch! Has the problem been solved after the board was replaced? And have you got a chance to test the voltage from the switch? I wondered it was 120 or 115?

[@diyhvacguy]

Yes the main power wire off the switch comes right from the transformer. So it had 122 as well. And yes the board fixed it. That board replacement video comes out tomorrow I believe. Showing how to physically replace the board 👍🏼 cheers

[@Nine_883]

I would just jumper 120v to that motor to run 24/7 until I could get a board so the customer doesn’t freeze. Depends what day it is and what time of day it is. Running it all of the time won’t hurt. Run it through a relay so high speed kicks out low speed. Whatever it takes.

[@diyhvacguy]

Yea I asked them if they wanted me to do that but it didn’t get cold that night so they said just leave it off. Thanks for the tip though! Maybe it will help someone else on here :)

[@Nine_883]

@@diyhvacguy Yeah for anyone who might be interested. Back in the day when we had the bimetal fan switch and a fan relay we jumped that low speed fan switch out all of the time. Let it run 24/7 and it actually would keep the house at a more even temperature and it would prevent it from short cycling. When the AC or "fan switch" was turned on the relay would kick out the low speed so there was never both windings energized at the same time. I even ran my own house like that and and the temperature was a lot more consistent. When PCB's took over the controls you saw that less and less because then you would have to add a relay to make it work. A lot of people prefer that low speed fan running all of the time. The fan only costs pennies a day to run (or at least it used to be pennies). This was very common practice back in the days before disco! 🤣😜

[@petersmart1999]

The voltage drop from the board is insignifigant,its plus or minus 10% 122 incoming to trans,an 115 out of board is not a problem. A bad fan relay on the board would be!

[@diyhvacguy]

The fan solenoid is before the heat pin for the fan, so how would the solenoid effect this if I’m getting 115 as soon as I hear the solenoid click?

[@petersmart1999]

@@diyhvacguy voltage is voltage,it can be present without current flow!

[@siroossoleimanian4813]

Thank for very good explanation and troubleshooting. Could you please explain TWIN terminal which no wire connected to? Also what is the replacement card for 4633e Emerson card for Amana furnace? Thanks.

[@zoubirgaoua7521]

Another great trick. Thanks

[@globalkonnect2059]

Cheat code thankyou

[@leelemon3373]

As always 5 Stars 😎

[@jimbarron8688]

Remove black wire from cooling speed terminal. Replace with yellow wire for heat speed. Select fan on at thermostat and call for heat. Fan will run continuously but heat will be on. Replace board... likely cause is pitted relay contacts in fan relay.

[@anhpham8199]

My blower motor won't start, but my unit is run by EMC Module. Can you help me fix it? Thanks so much.

[@6ecortes]

Great video. I have a Trane furnace that shuts off because the blower keeps shutting off. I found that by pressing on the control board the blower will kick in and I will have heat again until the process begins all over again. Do you have any idea why? New sub here.

[@giantkillin8278]

adding to my knowledge bank.@ thanks

[@GotchaplumberGotchahvac]

Question: When jumpering R & W, will the board allow the blower motor to come on without jumpering R/W/G?

[@sonle-fz1xb]

Great video! Thank you so much.

[@thomasmarshall7795]

Dave,replaced contractor in my Amana heat pump I thought all wires were replaced however I found 1 red wire that comes from defrost board marked cnt where on the contractor does it go? Thank you very much

[@terrellherrin1661]

So if all the wires to the thermostat have power, (24 vdc) the control board is bad?

[@anhpham8199]

My blower motor stopped working after a few days of running. It will start working again after I let it rest for a couple days. I suppose blower motor was over heat. How can I fix it? Please help.

[@bachphi1]

One of the relays is bad, its contact did not switch . If you pull out the blue and/or red, I think it will run.

[@Heyim18bro]

1:39 I think I added the jumpers while it was on and it blew out the blade fuse. Did that happen because it was on or is that an indication of something else?

[@Randylazz]

Pretty Cool Tech Tips………..

[@GotchaplumberGotchahvac]

Enjoy video.

[@cutum]

Crazy. You'd think 115 would fire up the motor

[@diyhvacguy]

I know right, I was stumped by this one. But my buddy learned me the safety switch truck 😎

[@eddieochoa6636]

Great video

[@LukeWarmwater-yb5lx]

Thank You.

[@vernardking8067]

My control board light is out and my unit not coming on my transformer isn’t getting any power

[@renecuevas4128]

Is there a misspelling on the price? Ridiculous i would get a 2nd opinion and pay a svc call....most is 300 for board and 185 install for a rep co. With a warranty 1 yr parts and labor and if u want old part i leave it on top of AC if part do not resolve the issue No charge for part only svc call but most our customers have contract so they only pay for parts not under cont.. about 100 bucks This ia my co in my state....lowest temp here now 56

[@stanleykania7184]

Nice !! Thank you

[@josephferguson3423]

Excellent

[@zurdohtown]

What happens if blower fan don’t stop

[@Discovery123.]

Question boss, did you go thru this career by apprenticeship program? I really like your video. Thanks!

[@diyhvacguy]

I learned most of what I know working with a friend of mine who had an hvac business back in Tennessee. Everything else has been self taught with the help of the Anti Diy Hvac channel as well as AC Service Tech! I did the 25 hr course to get your contractors license here in utah and took the test and that was it! Utah is really easy to get your license.

[@Discovery123.]

@@diyhvacguy Thank you Master!

[@planetvance]

What do you think of AirQuest vs. Goodman? HVAC Direct wants to substitute AirQuest for my Goodman order. Should I say OK?

[@diyhvacguy]

Yea Airquest is an offshoot of Carrier equipment. It’s a good brand and the same 10 year warranty can be had with Airquest. If you need some help with your replacement, check out our Patreon membership over at Patreon.com/diyhvacguy where for $50 I will give you one on one assistance with replacements, diagnosing, and even help with getting the full 10 year warranty on your equipment. Cheers

[@donhgr]

I been fooled by that before and you can see 115 mv and think it was volts and you really don’t have any, look closely at your meter when you see that because a lot of times it would run on 115 volts.

[@diyhvacguy]

What do you mean look closely?

[@donhgr]

@@diyhvacguy I missed it saying mv instead of volts and added 30 min to troubleshooting thinking I had AC,

[@elkess1]

How do you touch the yellow wire to the door switch while power is ON?

[@diyhvacguy]

Pull one lead off the door switch on the back and touch yellow to it while closing the door switch

[@derrtydungeon]

Zip screw🙏🏿👍🏿👍🏿

[@paulshlasko3608]

I don't think it was the 115 volts that was insufficient, I think it was lack of amperes.

[@diyhvacguy]

Interesting. Well the new board fixed it. I just wish I would have tried the fan motor to the safety switch trick before replacing the motor only to find out it was fine! Smh

[@paulshlasko3608]

@@diyhvacguy You did it right, I am just mentioning things I have stumbled over. The test meters read a voltage that sometimes has no real meaning because negligible amperage will make it through when an actual load is applied. I think if you read the voltage with the load applied, it would drop to zero. Conversely, I have made another mistake when I tried to test an electronic low voltage transformer. It read no output, but if you put a bulb to it the bulb would light and you could read the volts and amps. Its just a thing that happens when you test an electronic device with another. Its just my experience; I have no formal training.

[@vasileiosbakas9754]

I m confused, the heating speed sends 115 v and motor not running and after you send 115v and kicks on, how is this possible?

[@FranciscoPerez-th2hw]

When he applied 122 from the door switch it turned on

[@vasileiosbakas9754]

@@FranciscoPerez-th2hw 122 and 115 no difference

[@diyhvacguy]

Yea that’s what I thought, but there is a different. That was the point of this video. I learned a valuable lesson in testing the fan with the safety switch, that rules out the blower motor or capacitor being bad.

[@diyhvacguy]

I didn’t do the safety switch fan test the first time I diagnosed this, I just checked the board, saw 115v and went to the supply house and got a new blower motor. It was after I put a new one in and had the same problem that I knew it was the board. But had I done the safety switch test first I wouldn’t have had to do it twice!

[@vasileiosbakas9754]

@@diyhvacguy Have never seen this before, i d say it s a bad neutral but the neutral of the blower goes back to the board and it was checked ok. Glad you got it fixed still seems weird to me

[@takeiteasymac3206]

That filter is gross

[@denisvigil1538]

😂 idiot they are made that way

[@jesiscott6048]

Actually, your blower is not getting enough current. We know the control board's relay (for the yellow wire) is being turned on since you measured 115 VAC, so the relay contacts must be damaged! Just trying to send you my electrical knowledge in return for your great videos.

[@diyhvacguy]

Interesting!! Thank you sir

[@jesiscott6048]

I'm female, but it's all good! Very cool how your video shows how there can be the expected voltage but far too little current(amps) to run a motor.

[@bachphi1]

The reason it did not get enough current because one of the other 'bad' relays. Pull out the red and or blue wire.

[@jollyscaria1922]

Bad bored ok damge power burinv ok replcing ssme modrls power high low voltges checking

[@HoodHandyman]

Im still not sure its the board.

[@diyhvacguy]

It was, the follow up video that hasn’t posted yet shows how to replace the board and that was indeed what was wrong. Bizarre right? I put a blower motor in because I didn’t think to jump it from the hot wire at the safety switch until a friend of mine told me about that. After putting the new blower motor in, same thing. Sometimes ya gotta do things twice I guess! Cheers man

[@diyhvacguy]

You’d think 115v would be sufficient but it wasn’t

[@HoodHandyman]

@@diyhvacguy I'm no major expert nor do i pretend to be but I would check the continuity on the wire before changing the board I am epa certified and have a diploma in HVAC :)

[@MrConcord75]

@@diyhvacguy you’re correct. If the main voltage is 122 and you’re seeing 115 at the relay it’s a sign of voltage drop. I bet if you measured the voltage at the motor connector with the motor plugged in when triggered it would be even lower or zero because of the load.

[@vasileiosbakas9754]

@@HoodHandyman agree with you 100%

[@ericwilliams702]

That filter is bad

[@petersmart1999]

No,im sure its a carbon impregnated special order filter! Bahahaha

[@diyhvacguy]

You are correct. Carbon filter. They are good about keeping the filter changed, as crappy as the unit itself looks haha

[@alfonsobenitez8574]

The heat relay in the board is bad. Replace the board.