DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > HVAC blower turns on when system is off




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Old 06-21-2014, 10:02 AM  
Peterc
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Default HVAC blower turns on when system is off

My Goodman gas furnace/AC unit will turn on the blower fan when my thermostat is in the off position. I have attempted to reset by pulling the front panel of the thermostat off, raised the on temp for A/C far above the current room temp but fan continues to periodically turn on.
Any thoughts?
Thanks,
Peterc



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Old 06-21-2014, 10:32 AM  
Wuzzat?
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Intermittent short in the 'stat, wall wiring or furnace. If this happens often you have a good chance of tracing it down with a multimeter.



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Old 06-21-2014, 11:17 AM  
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Actually, depending on code in your area it may be neccessary for ventillation if you have a super insulated house.

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Old 06-21-2014, 11:58 AM  
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Today I have learned something. Numero uno pregunta in troubleshooting: is it designed to do this?

This particular feature should be listed in the 'stat manual so step number 0 in troubleshooting is: read all manuals.

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Old 06-22-2014, 09:40 AM  
Peterc
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Manuals read (about the 3rd time for various reasons) and find no reference to blower turning on automatically when system is off. The only similarity is the duration of time blower is on, about 2 minutes or the same as if the heat was initiated but the ignition did not take place.

Question: what is the 'stat wire?

Thanks, Peterc

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Old 06-22-2014, 10:52 AM  
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Quote:
Originally Posted by Peterc View Post
the duration of time blower [you mean draft inducer motor?] is on, about 2 minutes or the same as if the heat was initiated but the ignition did not take place.

Question: what is the 'stat wire?

Thanks, Peterc
Sounds now like the problem is in your furnace and you have two minutes to trace down the source of that false signal, until the next time.
For this kind of problem I put appropriately wired LEDs on several test points and when the problem shows up the LEDs that are on or off tell pretty quickly where the problem is.
That's a little beyond DIY stuff.


'stat = t'stat = thermostat.
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Old 07-10-2014, 04:12 PM  
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With limited time to catch the fan on problem, I finally heard the air blowing/sucking from the vent pipes outside the house. I later identified that this happens WITHOUT after I disconnected the thermostat from the wall. I still can not find anything that says this is a normal function. Guess I'll bite the bullet and bring in the A/C people.

Thanks,PeterC

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Old 07-10-2014, 05:25 PM  
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Quote:
Originally Posted by Peterc View Post
With limited time to catch the fan on problem, I finally heard the air blowing/sucking from the vent pipes outside the house. I later identified that this happens WITHOUT after I disconnected the thermostat from the wall. I still can not find anything that says this is a normal function. Guess I'll bite the bullet and bring in the A/C people.

Thanks,PeterC
With your reproducible symptom the HVAC people should be able to give you estimates, the minimum expected, and the maximum expected, cost.

If their minimum is $100 and their maximum is the same as the price of a new furnace, they have told you nothing of value. The range is too wide.

It's not like they have no idea what's causing this.

Call at least five places.

Another option is to go to an HVAC parts place and ask what part for your furnace is sold the most often, and what is sold the least often.
I did this with a Stihl leaf blower: they are not DIY-friendly and I suspected the magneto but the parts guy said they hardly ever sell any of those. BTW, it was a $3 jet that a repairman for a rental place clued me onto.
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Old 07-10-2014, 10:58 PM  
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This is a very helpful video which takes you thru a diagnostic step-by-step.


If you cannot solve it with this approach, you might have to get a tech out to fix it.
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Old 07-11-2014, 01:40 PM  
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For outside HVAC work, I recommend
a dry board to step on so you aren't grounded
a flashlight, even in the daytime
a tray on the ground so you won't lose the small parts you will drop in the grass
insect repellent



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