Papermaker
New Member
Hello, have an American Standard Freedom 95 modulating furnace. Has an Emerson UltraTech variable speed 3.0 blower motor (generation 1). Unit is about 10 years old.
On call for cold, blower speeds up to maybe 60% for 30 seconds or so, slows to a stop for 5 seconds or so, then speeds back up and repeats this over and over. AC compressor running. Door open. Filters clean. With fiber camera, evaporator looks clean and unrestricted air flow to vents.
This happens only on a call for cold. If I shut the communicating thermostat to off, but fan on. Fan will run normal.
In frustration, I unplugged the communicating harness from the control board to the motor, while it was cycling as above on call for cold. I expected the motor to stop, but it continued cycling as described above with harness disconnected. Now that I found info on the motor, I will be checking communicating voltage in both cold call, and fan on conditions to see what I get tonight.
I don't understand yet why the motor kept cycling with the harness unplugged, but I am more suspect I have a control board problem, and not the ECM module on the motor (since motor behaves correctly with fan on and no call).
Has anyone debugged a similar problem on a variable speed blower? Where would you throw money first? Could it possibly be the communicating acculink thermostat itself?
Thanks
On call for cold, blower speeds up to maybe 60% for 30 seconds or so, slows to a stop for 5 seconds or so, then speeds back up and repeats this over and over. AC compressor running. Door open. Filters clean. With fiber camera, evaporator looks clean and unrestricted air flow to vents.
This happens only on a call for cold. If I shut the communicating thermostat to off, but fan on. Fan will run normal.
In frustration, I unplugged the communicating harness from the control board to the motor, while it was cycling as above on call for cold. I expected the motor to stop, but it continued cycling as described above with harness disconnected. Now that I found info on the motor, I will be checking communicating voltage in both cold call, and fan on conditions to see what I get tonight.
I don't understand yet why the motor kept cycling with the harness unplugged, but I am more suspect I have a control board problem, and not the ECM module on the motor (since motor behaves correctly with fan on and no call).
Has anyone debugged a similar problem on a variable speed blower? Where would you throw money first? Could it possibly be the communicating acculink thermostat itself?
Thanks
