My trane air heat pump handler motor doesn't come on. It has a buzz and ocillates back and forth trying to start it seems. This happens when in A/C, Heat or fan only mode. Heat pump cool and heat work fine. Checking the trouble shoot guide it seems it is likely the control module transformer but I don't know how to check it. I have a meter. The CFM LED on the control board is blinking rapidly for 10 secs then a 2 sec pause and blinks again. I think this indicates the fault but what? Any ideas please.
Colin

Is this a variable-speed motor? If so, what you describe is a common symptom of a failed speed-control module.

Hi KC13,
Many thanks for your reply. I think you may have nailed it! I have it removed. I checked the motor with a meter as described in the pdf attached and it checks OK. Is there a way to check it or must I replace the whole board and take my chances. It looks like expensive special order maybe or can I trust a local retail supplier if I can find one?

I have rarely seen the motor component fail. I test them in 3 ways: 1) At the 3-pin motor harness, check for equal continuity 1-2, 1-3, & 2-3. 2) Check 1, 2, & 3 for continuity to ground (the motor housing). You should read infinite resistance, indicating no ground short. 3) With the motor removed from the blower, turn the shaft by hand - you should encounter little resistance. Short 1-2 with a jumper wire & try to turn the shaft again. You should encounter increased resistance. Repeat this step for 1-3 & 2-3. If motor passes these tests, you can rule it out as the culprit. Do you see any visual evidence of electronic failure of the module, or detect a burnt odor from it? The pic you attached offers limited visibility of the internal components.

Hi again KC13,
I checked continuity as you described, all OK. I don't have the blower motor out. I am working top a ladder so hope to avoid but the motor/fan does turn freely by hand and there is no sign of bearing harshness, looseness or motor mounting problems. There is no visual or odor evidence of electronic component failure. I'm not sure how to do the jumper wire short test. How would I get the power there. It's a 200/230V motor.
Thanks for your time
Colin

You can perform the rotational resistance test by spinning the blower by hand, then jumpering the motor connector pins. The wheel should stop abruptly. This is not a test performed with power applied. You may see a small arc when you insert the jumper. This is not unusual, as the motor is acting as a generator in this way. If you can provide some additional pics of the inside of the module, I may be able to identify anything unusual. Look closely at the capacitors (black cylinders) for swelling or splitting of the plastic wrapper.

KC13
You know this stuff and I really appreciate your help. Attached 5 more pics. I see no signs of any problem there. I tried the jumpers. Because I am on a ladder (only room for me)and fan is stll attached I inserted the jumper and then spun the fan/motor. I get light braking effect when jumping 1-2 and definitely more, maybe twice as much, and equal braking when jumping 1-3 and 2-3.?

I see nothing obvious from the pics, but there are more electronics in the resin bed beneath the circuit board. The motor component checks out, and the rocking effect you observed is common when the module fails. Inspect the harness connectors and double-check the line voltage input to the unit. If you find nothing unusual, the module is bad.

Input voltage looks good. Reassembled all and no change so I guess I will call the local Trane service guy tomorrow and see if they can check it and maybe have one in stock. I found a genuine replacement on line from United parts supply for $442. Is that a fair price?

I might expect a price like that for the complete motor assembly, but that seems very high for the module alone. Then again, most of these that I encounter are Bryant & Carrier. Trane parts are notoriously more expensive. Why, I don't know. I would be compelled to do a little more searching before buying one from them.

Hi KC13, Great news! My system is running. It turns out the air handler 5 yr warranty is good to August 2011! I didn't catch this initially as I thought it was installed with the Heat Pump in 2001 when previous owner remodeled the house before I bought it. It was a good exercise for me to follow your trouble shooting guides. I was able to negotiate a very competitive labor charge with a local service company to confirm my diagnoses and replace the motor and control module on warranty. I paid $120 total labor. The module alone would have cost >$400. I am very happy with this outcome.
THANK YOU VERY MUCH for your time and expertise. If I have any problem in future I wouldn't hesitate to use this site and hope to have your level of knowledge available.
Best wishes.