Atwood Furnace Trying To Self Start
I have a Atwood Furnace AFMD30111. I just returned from a 3 day trip where the furnace was used a lot. Today when cleaning the trailer I heard a noise which sounded like a small fan. I finally tra...
Forum Discussion
Either the thermostat is shorted allowing 12VDC to signal furnace circuit board
OR
Circuit board is faulty
12VDC form Fused source goes to Furnace PWR on circuit board...12VDC + is always at the circuit board
**same DC goes to thermostat
When thermostat Closes the DC goes back to circuit board at 6 pin connector via Blue wire --- this triggers the BLW circuit to energize the FAN Motor
Another Blue wire is at that connector...it is from sail switch/limit switch circuit
This Blue wire should ONLY be hot when fan has come up to speed closing sail switch
So thermostat Has to be closed in order for DC to go back to circuit board....if OFF then it could be shorted
But with DC always at the circuit board PWR section... the circuit board could be faulty allowing DC to BLW section causing fan to run etc
Remove thermostat...disconnect either one of the Blue wires.
If Furnace stops then thermostat is shorted
If furnace continues to run...then circuit board is faulty
See Pg 8 for wiring diagram
OR
Circuit board is faulty
12VDC form Fused source goes to Furnace PWR on circuit board...12VDC + is always at the circuit board
**same DC goes to thermostat
When thermostat Closes the DC goes back to circuit board at 6 pin connector via Blue wire --- this triggers the BLW circuit to energize the FAN Motor
Another Blue wire is at that connector...it is from sail switch/limit switch circuit
This Blue wire should ONLY be hot when fan has come up to speed closing sail switch
So thermostat Has to be closed in order for DC to go back to circuit board....if OFF then it could be shorted
But with DC always at the circuit board PWR section... the circuit board could be faulty allowing DC to BLW section causing fan to run etc
Remove thermostat...disconnect either one of the Blue wires.
If Furnace stops then thermostat is shorted
If furnace continues to run...then circuit board is faulty
See Pg 8 for wiring diagram
