Furnace and AC Fan Not Working! Troubleshoot the Fan Control
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- čas přidán 28. 07. 2024
- In this HVAC Troubleshooting Video I show you how the Fan Control works in Boilers, Furnaces, and Air Conditioning units for Troubleshooting why the Blower Motor is not Working and during the Heat or A/C cycle. I show you the voltage flow from the door switch through the fan limit and to the fan control which includes the general-purpose relay and back out to power the blower motor. I also show you the fan limit control and how it powers the fan during heat mode and where the fan limit is connected and how to read the voltage across it. I show you step by step what to check for until you get voltage through the controls and to the blower motor. Supervision is needed by a licensed HVAC Tech before doing this as Experience and Apprenticeship garners Wisdom and Safety.
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Finished my associates in hvac. I've been working as service tech in the field for one year. I watched your videos all through college and I still do! Excellent channel !
That's awesome to hear, thanks Jason!
I went from a Togami magnetic connector someone installed to a Zettler, without your video I would of been Totally screwed on wiring it in. I can’t thank you enough for the very clear breakdown!! Double thumbs up 👍🏻👍🏻
This was like the best teaching video I have seen the way you explain things please do more like this
My grandmother has that exact same control setup on her 50+ year old furnace. I've seen a few younger HVAC techs get stumped by that old setup and end up walking away (no charge) since they couldn't fix the problem 😁
The funniest one was the leaky pilot tube that would initially light the pilot (universal combination gas valve) and then the main gas valve would open and work perfectly until it stopped called for heat.
When the main gas valve opened the leaky pilot tube would ignite underneath and when the main valve closed it would always snuff the pilot light out like clockwork.
I watched several techs switch out the combination valve with no success. The best one though was the tech who installed an White-Rodgers (Thermocouple Actuated Line Interrupter) gas valve and didn't jumper out the ECO terminals. Basically, he messed around with the gas valve for about 30 minutes before giving up. If he'd just read the directions and used the supplied jumper wire, he could of at least got the pilot light to work before leaving 🤣
Sadly, I ended up having to fix the problem and now I'm stuck working on it because my grandmother won't call any of the local HVAC companies anymore since most of them are nothing more than a bunch of price gouging hacks 😖
An overall wiring disgram showing all the components you talk about connected would be nice. Thanks for a great video
Thanks for the excellent explanation. I am having this problem, heat goes on but the fan does not. The fan does turn ON when set to ON at thermostat though. Initially, I though the thermostat is bad, but now I understand the furnace/AC system has a separate mechanism that control the fan. These are very well explained in this video.
Watch this video again the 3-rd time today, now I understand my fan low speed does not work. With these explanations about the voltage path to identify which wire does what, I can track the voltage path in my furnace system and find out why the low speed does not work. Thanks a bunch.
Thanks for your videos, this saved me some $$$ as my unit went down and couldn't get anyone out to my home and especially when I told them I had a 1992 lennox unit. So I took to youtube and found your videos and was able to follow your guidance and figured out my transformer was bad. I was able to get the replacement and this fix my unit and I now have a warm home again! Thanks so much for sharing your knowledge for the diy homeowners like myself... thanks again!
Thanks for posting. Great video. I haven't ran across one of these yet, but now I am ready.. Thanks for your time.
Thank you Fred Mills!
had a call where the gas fired boiler was using a fan center , tstat was wired red and white to r and g on the fan center terminal buss. Not understanding why w terminal wasnt used instead of g had me going in circles for a bit. thanks for the information.
Thank you for a very detailed video.
Thanks Fred D!
Very thorough and clear! Great video appreciate the wisdom. Keep up the good work.
Thank you very much youngbeechnut78!
Thumbs up for a very well done video!
Thanks DC Rickerson!
Nice
The youngsters need to see this!
That was a little long winded,but needed if you have power to it and it doesn't work throw it out.
Nice👍
Stay safe.
Keyboard super tech.
Wear your safety glasses.
Great video dude,Very helpful and informative 👍 loved when you started tracing the wires 👀
Thanks a lot Thomas, I am glad you appreciated that!
This video really help me fix my furnace in one of my rental properties!
Thanks Antonio!
Thanks for this video,helped me a lot, very well explained
Outstanding explanation! I'm a total noob but your explanation made so much sense.
Thanks quantass!
thank you so much for another awesome tutorial video AC Service Tech.
Thanks!
That fan control center is old school.Great videos as always
There are a lot and I mean a lot of them out there still! Thanks
Great video!!! Keep them coming.
This was a great help for me, thank you.
Thanks Gilmer!
awesome, thank you. I am going to add a fan controller to my old oil furnace so I can control fan operation via a new tstat, This is exactly what I needed. I went a along and drew out a diagram as you explained it. Maybe you could re-upload with a diagram shown at the end.
Great trouble shooting video..Thank you
Thanks Riad Alshobaki!
Thanks great video really helpful
Thanks Terrell!
thanks for posting this,I never see these because I do commercial
Thanks Capitol!
😮 love this video
great channel!
Thanks Kemon Papadimitriou!
great video.
Thanks Krzysztof Fekieta!
It appears that the red wire from the limit switch goes into a wire nut and spits to power both the transformer primary and the pole terminal of the SPDT relay. If that's the case, when the limit opens the burner will turn off as expected but also the blower will turn off which isn't ideal as the blower helps to cool off the furnace when it cycles on the limit switch.
Thanks!
Thanks Jeff!
semper fi...verrrryyy goood info
Thank you very much myplace!
The red from the limit connects the 2 black wires should I add an additional hot from that hub to power the oil primary control
Thanks for video, you always do an excellent job. I was wondering what the name of the Fan Control Center Relay you are using, is it a White-Rogers 90-112? Thanks
I believe it was, thanks
another awesome video, how long have you been a tech?
Thank you JDT738126! I have been an HVAC tech for 14 years. Time flies!
If the white common on the back of the transformer was hooked to ground would it still work?
The red wire going to my thermostat has 27vac and the white wire coming back only has 13vac. What would cause this?
Hi, you explained that out of no. 3 terminal in relay (Red) you connect it to the blower motor.... but im confused because when you call for heat the blue wire out of the fan/limit control you also connected to the blower motor.
Dont get this part. When G is energizes coil it closes relay contacts 1-3 i get this part. Line voltage goes through fan limit and then wired to terminal 1 on the relay, right?... and 3 goes to blower motor (120 hot!) either high, med, or low speed, right? but then in heating what, out of the limit you said the blue wire also goes connected to the blower motor and i would assume o terminal 3 on the relay? how so how is this possible ?
Is it a way you can bypass the limit if it doesn't work
I am working on a an oil furnace. the AC stopped working. I changed the relay and still the AC is not turning on. Does the fan limit switch has anything to do with it? Thanks for your help.
You should have a multipurpose relay or fan relay that controls it. You would need to see if you read 24v from y to c at the control inside the unit when the tstat is calling for cooling, thanks
Do you fan control relay
I got a 30yr old york furnace that doesnt have general purpose relay.just has a transformer were you connect tstat wires like transformer on your video,I isolated the thermostat & the blower motor keeps running,what can it be?i have to turn breaker off manually,i replaced capacitor, spark igniter board & still same issue,i took common wire that comes from transformer goin to capacitor off & thats the only way it turns off,plz help
Look up "acservicetech fan limit control" thanks
Can and why is a buzzing sound coming from fan relay? I just replaced it 2 weeks ago. Also ( coil) it is hot to the touch. I'm assuming it was because my ac unit outside was on but my fan wasn't working. I also noticed the coil? Was not completely plugged in. After letting it cool i plugged it back in and powering back on it worked fine. Just the buzzing noise now. Help! Wifey hates heat!!! 😂 P.S. do i have to worry about an fire hazard in thymus instance? I'm testing the capacitor next.
Does the noise still happen when you remove the relay part and just have the transformer powered? Most of the time it is the transformer. You should check amperage on the tstat wires or just go ahead and replace the whole fan relay assembly it sounds, thanks
AC Service Tech LLC i removed the top part(transformer) still buzzing. Thanks for responding! Still buzzing although system running. Constant buzz even after a/c recycles.
What if my limit wire goes up to furnace
You could show the wiring schematics. It would be easier to understand.
My new tv show.
Thanks eclipse!
Similar to ice cube relay
Yeah all relays really work the same way, thanks
I have a white rodgers 90-112 fan control transformer/relay assembly. I have a white wire coming from the C terminal on my A-1 components fan blower control module and I am unsure where to connect this to on my transformer, it looked like they had it connected to the C terminal on the transformer but the terminal was loose so when I moved it the wire just came off. Some amateur HVAC guys came in and did a number on my unit and actually bypassed my power vent system so my vent didn't work, as well as disconnected my 24v wires from the condenser unit outside (would like to know where these go as well). Please help..
I just start changing parts,hoping I eventually fix problem lol
Uh oh yeah the newer furnaces you cant parts change as the control boards and variable speed motors are expensive and harder to get your hands on. Good Luck, thanks Chad!