RE: variable speed motor on york heater is defective

So this post is in response to this post I made a long time ago...

http://www.houserepairtalk.com/showthread.php?t=3275

Anyway I finally got around to making videos about repairing this problem

Here is a video showing how to replace the Thermistor in the motor
https://youtu.be/yEtuwNr0AZM

And here is how to take out the blower assembly
https://youtu.be/tRvqHeFzIiE

Hopefully these videos can help someone that has a similar problem...

So when this problem first occurred I purchased a replacement motor and after about 2 years the replacement motor had the same exact failure, so I figured out I could just purchase a new Thermistor and solder it onto the motor. I did that and it fixed the problem on both motors, however both motors still consistently fail after about 2 to 3 years of use, so since my last post I have soldered on replacement Thermistors about 3 or 4 times every two years.

Anyway, I hope this can be helpful to some people out there, so you dont waste thousands on repairs when all you need to do is replace a $5 Thermistor...

That looks like good info. But how did you determine what the problem was?

Thanks for the informative post. :thbup:

nealtw said:

That looks like good info. But how did you determine what the problem was?

Click to expand...

Just basic troubleshooting mostly, when the problem first occurred....

This is a gas furnace so when it stopped blowing air I noticed that the gas would still flow and start to burn when the temp in the house went below what was set on the thermostat. But, after a couple of minutes of the gas burning inside the furnace the flames would go out because the blower fan would never start spinning (this you could see without even taking apart anything just being next to the furnace you could see/hear it happen).

So just based on this I knew the problem had to be either with the power supply/circuit board that controls the motor or the blower motor itself.

So as you can see in the video above when I first took it apart I inspected that power supply box and looked at the circuit boards inside and everything looked ok. So next I took out the motor and when I took it apart I could clearly see one of the components had burn marks on it, so I figured that was it. At the time I did not know this was a thermistor and could not find one online just with the part number that was written on it, so I ended up buying another motor and that fixed the problem (I tried just buying that control circuit on the back of the motor but could not find it either).

Later I checked this forum again and someone had said that this is a thermistor (in my original post), so I ordered it online and replaced it in the old motor. When my new motor failed a couple of years later, I swapped in the old motor again this time with a new thermistor, and it worked.

Thanks I thought you might have done some fancy diagnostic or something.
So visual only got you there. Sound like the cause is in design if it happens to the next motor too.

Nice work. But the question becomes " why does the thermistor blow?"