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Rick Amos
Rick Amos,
Category: HVAC
Satisfied Customers: 2
Experience:  Owner at The Comfort Zone
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My name is ***** *****. My Fan on my furnace will not stop

Customer Question

My name is ***** *****. My Fan on my furnace will not stop running.
JA: Thanks. Can you give me any more details about your issue?
Customer: well at the thermostat I can set everything to OFF and the fan continues. the only way to turn it off is by the switch next to the furnace I tried replacing the control thermostat in the living room with a Nest thinking that the thermostat mechanical switch was faulty oddly, when I installed the Nest it did not power-up. This makes me think the low-voltage coming from the furnace is not coming up to the thermostat
JA: OK got it. Last thing — HVAC Technicians generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 11 months ago.
Category: HVAC
Customer: replied 11 months ago.
BTW - I checked the 5A fuse on the Fan Control module and that is fine. Also, the fan turns off when you remove the furnace cover (cover switch works).
Customer: replied 11 months ago.
Unit is a Tempstar gas forced air unit installed in 2000
Customer: replied 11 months ago.
Here is wiring diagram
Customer: replied 11 months ago.
And furnace model #
Expert:  Gaztech replied 11 months ago.
Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue.If my initial response doesn’t answer your question then let me know and we can continue our conversation.NOTE: I can only get paid for assisting you if you click FINISHED and RATE ANSWER after you are satisfied with answer.Are you ready?
Expert:  Gaztech replied 11 months ago.
Can you set your t-stat at OFF and fan mode to AUTO, then remove door cover on furnace- In the bottom compartment of furnace locate control board where the t-stat wires connects.- remove the wire on terminal G, then press in door switch to see if fan will stay off.
Customer: replied 11 months ago.
Hi Sorry - I am not in front of furnace, can you provide some instructions here and when I get home (after work I can execute your instructions?
Expert:  Gaztech replied 11 months ago.
Can you set your t-stat at OFF and fan mode to AUTO, then remove door cover on furnace- In the bottom compartment of furnace locate control board where the t-stat wires connects.- remove the wire on terminal G, then press in door switch to see if fan will stay off.Do this part and reply to this page to continue troubleshooting.OK?
Customer: replied 11 months ago.
BTW - I have a voltmeter if that is needed.
Expert:  Gaztech replied 11 months ago.
Good!!
Customer: replied 11 months ago.
Hi
I removed the Green wire from the control terminal and pressed the door switch - upon pressing door switch the fan started up again.
Customer: replied 11 months ago.
what should I try next?
Expert:  Gaztech replied 11 months ago.
if you...set your t-stat at OFF and fan mode to AUTO, removed wire on G and still blowing, replace control board of furnace.
Customer: replied 11 months ago.
Is there anyway to repair the board? replace a transformer or something along those lines? If you do not think this is a good option, can you suggest an on-line store to purchase replacement control board? Thanks!
Expert:  Gaztech replied 11 months ago.
if you...set your t-stat at OFF and fan mode to AUTO, removed wire on G and still blowing,replace control board of furnace.
Customer: replied 11 months ago.
Ordered replacement board. - thanks
Expert:  Gaztech replied 11 months ago.
It was a pleasure to help you out with that, nowNOTE: I can only get paid for assisting you if you click FINISHED and RATE ANSWER after you are satisfied with answer.
Customer: replied 11 months ago.
Hi Luke - as you recommended I replaced the control board and I still have the same behavior/problem. Fan continuously runs and I do not seem to have power at the T-stat (Nest). What do you recommend now?
Expert:  Gaztech replied 11 months ago.
Ok I reviewed all details given and have come to a conclusion1- The switch you say, by the furnace? It is a switch that was added by instalers on to activate fan continuously at a low speed and it would be normal operation that fan stay on all the time when switch is activated, if it was set to off, the fan would only run upon t-stat or furnace demand. 2- The NEST t-stat requires a common wire connected to C terminal for it to work, your old t-stat probably did not require that. You need a wire from furnace at terminal C to t-stat C terminal.
Customer: replied 11 months ago.
Hi Luke - Below I have some comments to your last reply.25 April 2016 08:11HVAC Technician
Ok I reviewed all details given and have come to a conclusion
1- The switch you say, by the furnace? It is a switch that was added by instalers on to activate fan continuously at a low speed and it would be normal operation that fan stay on all the time when switch is activated, if it was set to off, the fan would only run upon t-stat or furnace demand. No, this is just a switch that turn AC on/off to the entire unit. The furnace will only operate when this switch is in the on position. I have a 2nd identical furnace next to the one with the issue and it operates as it is suppose to when the switch is in the "on" position.2- The NEST t-stat requires a common wire connected to C terminal for it to work, your old t-stat probably did not require that.
You need a wire from furnace at terminal C to t-stat C terminal. Though this is something I can check, I do not think this is the issue. I didn't indicate previously, but I bought the nest "after" this issue with the furnace occurred. I had been wanting one so I used this opportunity to swap the old T-Stat in the event that was the source of the issue. Anyway, point is I can swap back the old T-Stat to eliminate the "Nest" issue - but I do not think this is the issue. BTW - I can also use the voltmeter to determine if the low-voltage control lines to TSTAT have voltage. What voltage should be on each line/color?The only thing left is the transformer and the CAP shown in these pictures (attached). The transformer would explain why there is no power to the control board and hence the TSTAT low voltage is not available to the TSTAT. Not sure the function of the CAP. Any thoughts on bad transformer as source of issue? What voltage should be at transformer primary? Secondary?Thanks for your insights.Carl
Customer: replied 11 months ago.
Here are the attachments referenced earlier
Expert:  Gaztech replied 11 months ago.
Hello, as you can see clearly on the transformer, the primary voltage is 115 V and secondary is 24 V That would have been the first thing you should of checked before changing any parts on your furnace.The capacitor is used to assist your blower motor, If is measured with a Microfarad tester. if it was defective the blower motor would not work properly.
Customer: replied 11 months ago.
Luke - " That would have been the first thing you should of checked before changing any parts on your furnace."
That is not the guidance you provided - please review this correspondence. Upon removal of the green TSTAT Control wire - your recommendation was to replace the control board.
Expert:  Gaztech replied 11 months ago.
As we are not onsite to do our own diagnosis, details become very important when assisting a customer via texting, I am here to assist you the best I can while sometimes dealing with more than one customer. Sometime a distraction can interfere in a thurow diagnosis,Hence; "Hi Sorry - I am not in front of furnace, can you provide some instructions here and when I get home (after work I can execute your instructions?"I should of asked you if you had checked for 24V at the board with your volt meter .Therefore I imagine you will be measuring the voltage when you get home and hopefully resolve the issue.SincerelyGaztech1
Customer: replied 11 months ago.
thanks Luke - I'll let you know what I find.
Expert:  Gaztech replied 11 months ago.
Have a good day !!
Customer: replied 11 months ago.
ok Luke we are going to get this solved. Here is some new info. I measured 24VAC across the Blue Yellow of the transformer. However, this was unloaded. When I plugged the transformer in I then measured Whte/Red and Whte/Yellow at the T-Stat terminal on the control board @ 0VAC. Of course I had the power to the furnace on and the door switch enabled (ie. the fan was running) when I took these readings.As I mentioned, I have an identical furnace next to the one with the issue. I measured at the T-Stat terminal Whte/Red and got 30VAC.Does this help narrow things down? Remember I have already replaced the control board (so I assume this is good). Is there somewhere else on the control board I should take a measurement? Or, is there some other "Switch" that would trip the fan and remove the low-voltage at the Tstat terminal? The only thing I can think of is the 24V Transformer (when loaded) fails and hence 0VAC at the TSTAT Terminal. What do you think?
Customer: replied 11 months ago.
Crickets???
Expert:  Rick Amos replied 11 months ago.
Hey Luke. Im Rick.Id like to take a stab at your problem.
Customer: replied 11 months ago.
Any guidance welcomed...I have ordered a xfrmr, hopefully will get by Sat. After I swap that, not sure what is left. As I mentioned before, I have a new control bd, I measure 24vac across the unloaded xfrmr, but when I connect to control bd I have 0vac at stat terminal on ctrl bd. This led me to believe the xfrmr is failing when loaded. Thoughts?
Expert:  Rick Amos replied 11 months ago.
crap it just erased a long message. ill typ it again
Expert:  Rick Amos replied 11 months ago.
ok so lets start with the thermostat.With your volt meter set to ac volts and auto rangeWhat do you get between terminals R and C
Expert:  Rick Amos replied 11 months ago.
ok im reading the rest of your commentsi believe your furnace is in a lockout.
Expert:  Rick Amos replied 11 months ago.
id like to help you. i can stay on if you will respond. Otherwise im going to sign off shortly.I see several possibilities for a resolution to your problem.
Expert:  Rick Amos replied 11 months ago.
Id be glad to talk to you on the phone if youd like. But im only available for the next few minutes.
Customer: replied 11 months ago.
0vac between r&c while fan is running
Customer: replied 11 months ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Rick Amos replied 11 months ago.
im still here if youd rather chat. Im logging off in two minutes if no response.
Expert:  Rick Amos replied 11 months ago.
ok to tell you the truth it sounds like your thermostat wire has been compromised. IE: a nail from a picture hanging or a pinch from some obstruction. If that doesnt pan out you have two separate problems. A phone call will be speedier. I will check your responses in the morning.

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