lugnut
04-10-2010, 11:47 AM
I don't work on Trane Rtu's, but I have one that I looked at today. I don't have a model number (sorry), but it's a 7 ton unit, about 8 yr old. When I arrived, I found the blower fan starting and running (in econo mode) for several minutes, then the blower drops out for a couple of minutes and the cycle repeats.
Always see solid green led on both econ board and rtrm board, even as I left the job. Put unit into test mode, and first step (blower test) did not energize the blower, (no errors flashes). I though it was a 24 volt short to ground because I got 12 volt readings across the fan contacter coil when the fan contactor dropped out, but despite this, more importantly, I feel the symptom cycle was too well timed to be a random short in the wiring. I did not time the events, but the entire cycle was under 10 minutes, maybe even less. I saw this happen at least 3 or more times.
After 30 min of poking around, the symptoms changed without any cause. I had not changed anything on the unit, then, instead of the blower starting intermittently as described, the rtrm board is making a very loud buzzing noise, from the tall canister part soldered to the board. Still have no alarms or error codes. Had to shut unit off to stop the buzzing. Any one ever heard this buzzing from the rtrm before?
The oa temp was around 57, in case anyone is thinking of a emerg stop due to frost, etc.
Always see solid green led on both econ board and rtrm board, even as I left the job. Put unit into test mode, and first step (blower test) did not energize the blower, (no errors flashes). I though it was a 24 volt short to ground because I got 12 volt readings across the fan contacter coil when the fan contactor dropped out, but despite this, more importantly, I feel the symptom cycle was too well timed to be a random short in the wiring. I did not time the events, but the entire cycle was under 10 minutes, maybe even less. I saw this happen at least 3 or more times.
After 30 min of poking around, the symptoms changed without any cause. I had not changed anything on the unit, then, instead of the blower starting intermittently as described, the rtrm board is making a very loud buzzing noise, from the tall canister part soldered to the board. Still have no alarms or error codes. Had to shut unit off to stop the buzzing. Any one ever heard this buzzing from the rtrm before?
The oa temp was around 57, in case anyone is thinking of a emerg stop due to frost, etc.