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Discussion Starter · #1 ·
Hi looking for some technical help with our HVAC system. I just replaced the blower motor in our furnace and it is running constantly since the change. I’ve disconnected it from the thermostat to isolate the problem and it still fires up as soon as the power comes on and stays that way with or without the furnace engaged. The furnace itself still turns on and off as normal so I don’t think it’s the furnace limit controller reading overheat or going bad. I suspect it could be a bad relay. The thing that really confuses me is that every morning when I wake up it tends to be off and stays that way until triggered either by the thermostat, the fresh air exchange or even me cutting the power and turning it back on gets it going again. Then it stays running until the next morning again.
 

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hvac techs should be along soon. Check out link (at bottom) for some basic trouble shooting tips. Has to be something you did or didn't do as its running constantly after the change.

Hope you get it figured out and working right soon. nathang. btw, welcome to the forums.

Why Does My Furnace Fan Keep Running?
 

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Discussion Starter · #3 ·
hvac techs should be along soon. Check out link (at bottom) for some basic trouble shooting tips. Has to be something you did or didn't do as its running constantly after the change.

Hope you get it figured out and working right soon. nathang. btw, welcome to the forums.

Why Does My Furnace Fan Keep Running?
Thanks for the welcome! Looking forward to hearing from the pros. I’ve been to about every forum trying to figure this out.
 

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Its possible the blower relay on the control board is sticking closed.

Its also possible you miss wired it. Post a pic of the wiring.
 
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Discussion Starter · #7 ·
Its possible the blower relay on the control board is sticking closed.

Its also possible you miss wired it. Post a pic of the wiring.
I didn’t actual do any wiring other than plug the new fan motor into it’s socket. but there was a technician here diagnosing the issue before, he replaced a circuit breaker and was able to tell that it was the fan that was the problem. I suppose he could have done something to force it to run in his testing.
635736

I have tested disconnecting the fan wire and it does not turn it off. In fact I tried disconnecting all the wires on this panel from the thermostat, heat pump, and fresh air exchange and it still just kept blowing.
 

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You gave me the model of a heat strip, not the "furnace".
It's a air handler with electric heat.

Could be a stuck relay or bad heat sequencer.
Would need to get schematic of air handler to know where to start.
 

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Could be the fan sequencer is sticking shut. That wasn't an uncommon problem on older units like yours.
 
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Discussion Starter · #10 ·
You gave me the model of a heat strip, not the "furnace".
It's a air handler with electric heat.

Could be a stuck relay or bad heat sequencer.
Would need to get schematic of air handler to know where to start.
Sorry about that! There are a lot of model numbers on the paperwork and I must have grabbed the wrong one. Thanks for your patience with a newbie here.
Attached is the air handler and it’s schematics.
635739
 

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do you have a multi-meter and have you done anything electrical before?

Your unit does indeed have a time delay relay/sequencer.

If power is removed and the relay reads closed with a meter minutes later, it's bad for sure.
 

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Locate the time delay relay.

Remove power and wait a couple of minutes (they time the fan off I believe).
Disconnect the wires connected to terminals 1 and 3 on that relay and check the resistance across.

If you don't read open line, replace the part. You may need to cross reference it.

You can try tapping on it.
 

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Discussion Starter · #15 ·
Locate the time delay relay.

Remove power and wait a couple of minutes (they time the fan off I believe).
Disconnect the wires connected to terminals 1 and 3 on that relay and check the resistance across.

If you don't read open line, replace the part. You may need to cross reference it.

You can try tapping on it.
Thank you so much for this. Very helpful. I checked 2 relays as I can’t tell which one is the time delay. The one pictured here shows a resistance of 69 between 1 and 3. It has relay contacts labels 1,2,3,4&5
It has a large blue cable numbered 4 on contact 2.
635749


The other relay is larger and feeds the lettered terminals (W1, W2, R, G, etc) that lead with colored wires to the thermostat. It has contact numbers 1,2,3,4,5,6 and has a small circuit board underneath it. The terminals labels 1 & 3 read OL with cables disconnected. It is pictured here with cables 1&3 dis
635750


can you help me understand which one would be the timedelay relay? The more I study the schematic the more confused I get 😅
 

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they look like this but you may have something different:



it's hard to tell without being there.

the main manual for your air handler shows time delay relay but there can be different revisions.

You should be able to find what's controlling the fan by tracing the wires.
 

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Discussion Starter · #17 ·
they look like this but you may have something different:



it's hard to tell without being there.

the main manual for your air handler shows time delay relay but there can be different revisions.

You should be able to find what's controlling the fan by tracing the wires.
Ok, I followed the wires and the blower motor wires run directly to the relay with the small circuit board attached to the bottom. Now that I know what I'm looking for (thank you!) I found the time delay relay model in the paperwork for the unit. It appears that the circuit board i'm seeing is the time delay relay. It looks like this:
635758

RLY1169
It is attached to the bottom of the relay that i tested contacts 1&3 on and found that they read OL. Should I try to pull this off and test it separately?
 

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So the relay isn't sticking closed.


To verify, disconnect the wire going from terminal 3 to the fan, put it in a place where it can't contact metal and restore power. The fan should not run like this.

To my knowledge, that relay brings the fan on for both heating and cooling. If I'm wrong and heating fan is brought on by heat kit as well in parallel or something, you'll have to look elsewhere.
 

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Discussion Starter · #19 ·
Ok, I followed the wires and the blower motor wires run directly to the relay with the small circuit board attached to the bottom. Now that I know what I'm looking for (thank you!) I found the time delay relay model in the paperwork for the unit. It appears that the circuit board i'm seeing is the time delay relay. It looks like this: View attachment 635758
RLY1169
It is attached to the bottom of the relay that i tested contacts 1&3 on and found that they read OL. Should I try to pull this off and test it separately?
Sorry, Looks like this might be the wrong part. Here is the one in the unit
635760
 
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