Been an exciting few days around here. I posted a while back with a blower that didn't run and I thought a diagnostic code, but I was looking at the wrong LED. The diagnostic LED never showed anything wrong. It's a Trane XV80 air handler with variable speed blower. And the blower varies it's speed constantly now.
It's one of those annoying intermittent problems. It works fine late night and early morning, then in the afternoon it starts. The blower seems to startup and shutdown constantly. Sometimes pausing a few seconds and then starting up again, only to stop half way to full power and ramp back down again, then startup and run fine for a few minutes and ramp down to half, then back up to full. and over and over.
The HVAC tech was out this morning, but of course it wasn't doing it then. He's ordered a new motor for me which should be in in a couple of days, until then it continues to cool OK in the night and less so good in the afternoon under high load.
My worry is that it will quit entirely and damage the outside compressor which appears to continue to run while the blower goes up and down.
Has anybody heard of such a thing and might have some further advice I can pass on to the tech? Is there a way to see if it's the motor or the control board? Right now he's just ordered a motor, but he didn't really know about the board. I asked him and he said that the controller was inside the motor. But I dont' think thats the case, or you wouldn't need so many wires running out of the motor.
ecm motor extremely.costly.motor. control on the motor
is the jumper from y1 to ds in place
read the install book on the unit
sounds like a low voltage problem and the motor control is searching for a signal
what typr stat do you have and does it have humidity control
The motor runs, its not bad. The module on the end may be faulty or a loose connection from the blower control board is more likley.
The motors themselves very rarely fail. Usually it is the module on the end of the motor, wich can be replaced without replacing the motor.
I can't say as I have ever seen one do what you describe exactly, but I have seen one that continuously started and stopped, and would jerk around a lot.
The problem was with the motor module.
I spoke on the phone just now with another guy from the local HVAC company and he and I are in agreement that it sounds more like the module. So he's ordering me a new module which will take a couple of days to come in and cost me a few hundred bucks to install. Can't do without the AC though
I'm still going to verify the low voltage side and the motor connections this evening if the temp in the attic manages to drop below 95 or so...
I could definitely hear something in the thermostat as the fan cycled up and down. It wasn't the loud click of the relays, but a much quieter click sound. Just to be sure I put the old Thermostat back on 2 days ago, but after turning the furnace back on the problem continued, so at least I ruled out a faulty thermostat.
Now that the new part is on order it will probably run perfectly and never show the problem again, either that or it's dead right now and I haven't noticed yet...
I managed to dig up the paperwork and it doesn't look like these are under warranty anymore, they were installed in '99 and only came with a 1 year warranty at that point and the previous home owners here did not purchase an extension (which would have run out by now anyway) so I'll be paying for it, but if it fixes the problem I don't mind.