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rtz
Aug 17, 2009, 11:17 AM
Okay, so the heating/ac guy cannot get out for a few days, so I started diagnosing things myself.

My blower (rheem residential gas/ac unit, less than 6 years old) was slowing down and finally quit. I had the motor checked out and it was dead at this point (very dirty, had been running on very dirty filter for awhile). I bought a replacement and got the appropriate run coil for the new motor. I put everything together and power it up - ac unit starts cooling, but the blower still doesn't kick on. I hear no huming, everything spins freely, board lights up fine, etc. Furnace is set with the "fan on" position so that it should be powering up right away, but nothing.

I checked for voltage going to the motor and am getting nothing on any of the 4 wires (red, black, blue, or yellow) going to the motor (using white as my common). Are there any other possible issues here, or should I break down and replace the board next? I thought about desoldering the relays and replacing them but figured that I can get a board just as quickly, and it might not be the problem (I suppose I could check the other side of the relay and see if power is hitting the relay at all). Before I do anything else though, are there likely other issues I should be investigating first, or should I take the plunge and buy another controller board?

Also, can safely run the motor on direct 110v by bypassing the controller board just to push some cool air into the house for 20 minutes or so if needed (if heat reaches 100+ again?) I know this isn't the best solution, but I'm looking at another day till the controller board would arrive.

Any advice or suggestions would be greatly appreciated.
Thanks.

KoV-Pappy
Aug 17, 2009, 12:05 PM
If you can read shematics and it sounds like you can. Do a power trace back to fuse box if you have to.

Basically u measure power halfway back to the supply if no power, then go back farther.

If you know its at the boards... this sounds dumb but you did say its dirty. Get yourself a big erasure and scrub down all the solder connections after you make sure all power is off to the board. If there are any big capacitors on there make sure to bleed them first.

Once its clean check to see if the board has any cracks and that all connections are properly seated.

After that its component level. If you want to post a wireing diagram ill help you trouble shoot it heheh