Hi There,
The blower fan on my furnace is ON all the time.
The thermostat is in AUTO, I have disconnected all the thermostat wires both at the thermostat end and at the furnace and it is still on, so I don't think its the wiring nor the thermostat.
I can get heat when heat is called, so I don't think its a limit switch.
I am thinking I have a stuck relay?!? I have tapped all the relays on boards and nothing changes.
So I am thinking I have a faulty board?
What I am not sure is how to diagnose which board is the faulty one since there are 2 of them the ECM motor control board (ICP 1175594) and Furnace control board (ICP 1172809)
BTW, I verified the switch on my ECM motor control board was set on OFF for the fan, but whatever setting I put it in I can't get it to turn off, I am able to reduce the speed from high to low but thats about it.
Thanks in advance!
Based on your troubleshooting, I would agree that there is a fault with the control board. I attached a picture below. I'm not sure if this only applies to the PSC models, but make sure there is nothing connected to the CONT terminal on the control board. (Marked with a red arrow.)
I'm not 100% if the DC MTR terminal (Marked with a blue arrow) is supposed to be constantly powered with 115V, but you may want to check that with a multi meter. I suspect it's always powered with 115V and the P2 plug powers the ECM fan.
My guess would be the main control fan timer board is faulty.
ICP technical support - 1-800-458-6650
Thanks for the quick reply! I will check later on in the afternoon :)
By main control fan timer board did you mean the large one or the smaller board?
The large control board - ICP 1172809.
Thanks again for your help!
Although the board layout is slightly different than your diagram nothing was plugged to the CONT terminal I went ahead and ordered the board, I am hoping it will solve the issue.