Trane XV90 Inducer

[gbfromsd]

I got issues with this unit. Inducer failure code, 3flashes, on call for heat. Trane's literature refers you to an Inducer troubleshooting guide which our local rep could not locate . . . hmmph. I've narrowed the problem down to the inducer itself. A visual inspection reveals damaged circuit components on the control board however due to the price of the new inducer fan assembly (near 400clams), I need to be sure.

I got 115v into the inducer's control board, a good neutral, 13vdc off the main board. Hi to dcNeutral checks 11.9, Lo to dcNeutral checks 11.9 (WhiteRed, and WhiteOrange) seems to be the neutrals for either low fire or high fire.

On the main board status lamp blinks slowly, Inducer speed lamp blinks slowly. Call for heat, status lamp blinks rapidly, speed lamp goes out. After 10seconds or so, no inducer startup and the 3flash code.

Verified the condition and function of all other safeties including the inducer high temp safety (closed), inducer LPS open, HPS open, Hi Limit closed, rollout open.

What's missing here?

[BaldLoonie]

Good luck, those things are lemons. Which one is it? Board on the inducer or not?

May be that the inducer is working fine and just not pulling a vacuum. Put a manometer or magnahelic on the high fire pressure switch and see. Could be a cracked transition or cracked header on the secondary keeping the inducer from pulling enough vac. There's a service bulletin out on that, among other things.

Oh, if the model with inducer control on the main board, could be the board too. There's been at least 2 new boards made since that model was made. Complete model #, every digit, would tell.

[swat]

Get your magnehelic out and lok at your furnace service lit in the back of the furnace service book you got if you have been to that class. You will need to make sure it is venting properly. I had one in december that the new construction idiots put massive traps in the exhaust line and it collected water. Unit would come on and sound kinda like gurgling in the vent. Not a ton but enough. The varriable combustion blower section shouldget you the info you need to cross off what it isnt and show you what it is. If you havent done that stuff before you are looking at about an hours worth of slow methodical work and checking and double checking frequency going to the motor and static pressure reading off the hoses.

[gbfromsd]

The inducer's not even starting up. It's the model with the board right on the end of the motor shaft.

On call for heat, LED's on the main board as described. At the fast flashing, the inducer should start turning but doesn't. I've checked the inputs/outputs at the harness connected to the inducer board, findings as described earlier (115v, good neutral, 13vdc, Hi 11.9vdc, Lo 11.9vdc).

How can I surely tell if the inducer board/motor itself is bad seeing as it won't start turning at all?