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-   -   Blower motor in AC unit not coming on (http://www.diychatroom.com/f17/blower-motor-ac-unit-not-coming-155921/)

Big John Studd 09-05-2012 11:26 AM

Blower motor in AC unit not coming on
 
1 Attachment(s)
I have a Trane XE 80 that has decided to stop blowing cool air. The outdoor component seems to be working properly (ie. the fan motor starts up when I turn AC on at the thermostat), but the blower motor inside the house does not turn on. I opened up the Trane and found that the circuit board controlling things is an Intell-Ignition (part no. CNT03076). The red LED on the circuit board steadily blinks, which (I think) is as indication that it is operating properly...or at least it thinks it is operating properly. I removed the blower motor connections from the board and connected 120VAC directly to the motor and it ran just fine, so I think the blower motor is fine. So I am guessing the thermostat could be the problem. Does anybody have any ideas on how I could troubleshoot further before just replacing the thermostat? Does anyone know what the voltages should be on the inputs to the ignition controller for the various thermostat settings?

Thanks!!!

allthumbsdiy 09-05-2012 11:59 AM

How old is your unit? Have you done any work on it recently or did the motor just stop working all of sudden?

I would replace the capacitor first (it's only 8 bucks or so). Just make sure you do not accidentally discharge it by touching both terminals.

I replaced the capacitor and blower motor on my XL80 last year and its been working great. If you want to read the actual steps I used, just google "how-to-replace-a-trane-blower-motor" and you will see my blog post.

Doc Holliday 09-05-2012 12:00 PM

Look for the capacitor which is going to be attached somewhere near the motor such as on the outside of the blower housing. It'll have two wires to it coming from the motor.

Be careful as IF it is good it will be holding a charge. Tell tale signs that it's bad is the top is rounded or it's leaking an oily/jelly-ish residue. Other than that you'd need a meter that tests microfarads (MFD/UF) to test that cap. It's only an approximate $10-$15 part if that. You can simply remove that cap (again, careful to not touch the metal but simply pull the wires off) and take it with you to Grainger where they sell to the public. When you re-wire the new one in it does not matter which wire goes to which side of the capacitor.

Now if you have a meter than we can test the control board to see if it's giving 120 volts to the motor.

Big John Studd 09-05-2012 12:28 PM

Quote:

Originally Posted by allthumbsdiy (Post 1003745)
How old is your unit? Have you done any work on it recently or did the motor just stop working all of sudden?

It was in the house when we bought it a few years ago. House was built in the late 80's, and I am not sure if this is the original one or not. No I haven't done any work on it. It just stopped working.

Big John Studd 09-05-2012 12:33 PM

Quote:

Originally Posted by Doc Holliday (Post 1003748)
Now if you have a meter than we can test the control board to see if it's giving 120 volts to the motor.

I do have a handheld multimeter, so I can check that. Since the motor ran just fine when I connected 120 volts directly to it, I assumed the motor and capacitor were OK.

Marty S. 09-05-2012 06:20 PM

Quote:

Originally Posted by Big John Studd (Post 1003780)
I do have a handheld multimeter, so I can check that. Since the motor ran just fine when I connected 120 volts directly to it, I assumed the motor and capacitor were OK.

First check between G and C on that board to see if the thermostat is telling the blower to come on. If yes then check for 120 to the motor. This is soooo much easier when you folks have some basic tools,thanks for that.

Big John Studd 09-06-2012 09:52 AM

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I pulled the circuit board last night. It may to tough to see in the photos, but it looks like the smoke got let out of one of the relays. The PCB may also have been damaged along the way...not sure yet. I'm going to try just replacing that relay (JTN1AS-PA-F-DC24V), which is like a $3 part.

bob22 09-06-2012 02:37 PM

Let us know if it fixes it please.

Big John Studd 09-06-2012 05:37 PM

Turns out the relay was fine. The trace on the PCB was burnt. I jumped the burnt section with a small piece of copper, put the whole board back in, and everything works! Now I have to figure out a permanent fix. Not sure if I can repair the trace on the PCB or if I will have to buy a whole new board for $150. The jumper is kind of a rig job and certainly not safe for unattended use.

Big John Studd 10-05-2012 02:14 PM

Just to update...I was able to permanently repair the PCB. Right around the time I finished, some beautiful autumn weather rolled in, and there was really no need to run the AC. This past week the heat and humidity came back enough to run the AC during the afternoons. It has been running fine without issue!

PaliBob 10-05-2012 03:38 PM

John, You get a DIY Gold Star
Thanks for including the pictures
Also it's a good idea to include your location in your profile.

To add your location to your profile see more How-To


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