My blower fan will stutter start every now and then. I have an Armstrong gas furnace with A/C.

Yesterday, I dropped the temperature to 67, after having cooled to 69, and the blower wouldn't ramp up to speed. It would continue to do the following:

https://www.youtube.com/watch?v=juM709WX96w

There is no capacitor with this blower and I checked the thermistor to see if it was broken or burnt.

Any other ideas on what to check? I'm thinking it's the motor module.

 

Hi, it appears that the motor is running, is that squirrel cage thight on the motor shaft?
Geo

 

Thanks for the reply. The cage did not feel loose when I removed the blower. I pulled the motor from the blower to check the module, however. I was reading that the thermistor could be the culprit?

From the look of the module, I couldn't really see an issue. Do any of the soldering points look to be burnt? The middle one, which is slightly darker, does hold the thermistor. That part did not seem damaged on the other side.

Also, I never received any errors, with the red light, on the main board. Would an issue with the motor/module show up as an error on the main board?

What are yall's thoughts?

 

I’d ohm out the windings on the motor and check the motor bearings for handshaking. Then, if that proved ok, I’d clip that thermistor and jump it out, what can it hurt, it’s not under warranty I assume. If it runs, ok till it dies. Otherwise I’d look to either replace it or use a much cheaper motor like a psc motor. Many of these motors can’t replace the modules. Ohm your wiring harness for breaks too. But then again, that’s just me....

 

What's the full model number of the furnace?

I wouldn't change parts until you know what's wrong.

The first step is to determine if the board is delivering the correct signal to the module/motor.

If it is, it's most likely a module issue.

If the thermister was bad it wouldn't run at all. Unlikely the windings in the motor are bad either but no harm in ohming them out.

There are two types of ecm motor - x13 and fully featured variable speed.

The x13 motor is simple troubleshoot as it operates off of 24v signal from the board.

The variable speed gets a electronic signal from the board to tell it what cfm to deliver/the mode. The manufacturer's specific instructions must be followed to diagnose.

Her's some generic info in troubelshooting: https://yorkcentraltechtalk.wordpres...ooting-part-1/

If the motor is an x13 and bad, best option is to just put in a cheaper generic ecm motor like the mars azure. I wouldn't bother attempting a psc motor conversion on a furnace due to the need for creative wiring with relays.

The mars azure looks like a good replacement and is cheap enough.

If the motor is the variable ecm, can change the module separately but it needs to have specific programming for your furnace. May be hard to source.

Of course, check your warranty. It could be as long as 10 years.

 

Thanks for the responses! I missed those and ended up having a new thread located here:

https://www.doityourself.com/forum/a...d-culprit.html

I thought my issue may have been the lack of voltage, 15v, going to "G" from the 16 pin connector on the board. (The harness had continuity)

The problem was the motor module after testing the board for any other voltage issues to/from the thermostat and other pins/connectors. After installing a re-manufactured version, which was an exact match for my motor, the issue stopped completely.

I'm going to run some tests on the old module and see if it was a capacitor or the thermistor. I'm not suspecting the thermistor, however.