Furnace Short-Cycling
2018 Furnace - Atwood/Dometic model AFSD20141 is short-cycling. I tried the following everything: Jumped the thermostat jumped the high temp limit switch jumped the sail switch removed disch...
Forum Discussion
The ONLY way at this point is to have the LP pressure checked at the furnace. NOT doing this will just cause problems in diag.
1. Removing the exhaust tube decreases the separation of exhaust and fresh air intake.
2. So, when short cycling, the system NEVER shuts down, just stays running with short cycling?
3. You cannot bypass a Sail switch on most furnaces built in the past 5 years. IF you engage the Sail switch BEFORE the control module starts the fan, it will cause ignition problems. The newer Module boards are smart enough to know when the sail switch is closed before fan start up. Older Furnace boards you could keep the sail switch closed and the furnace would operate correctly for testing.
4. I would want to take a voltage check on the output side of the sail switch to see if it loses its 12 volt signal for a few seconds and then restores the signal which would cause short cycling. Which would mean a bad sail switch
5. This also points to a air volume restriction. Doug
1. Removing the exhaust tube decreases the separation of exhaust and fresh air intake.
2. So, when short cycling, the system NEVER shuts down, just stays running with short cycling?
3. You cannot bypass a Sail switch on most furnaces built in the past 5 years. IF you engage the Sail switch BEFORE the control module starts the fan, it will cause ignition problems. The newer Module boards are smart enough to know when the sail switch is closed before fan start up. Older Furnace boards you could keep the sail switch closed and the furnace would operate correctly for testing.
4. I would want to take a voltage check on the output side of the sail switch to see if it loses its 12 volt signal for a few seconds and then restores the signal which would cause short cycling. Which would mean a bad sail switch
5. This also points to a air volume restriction. Doug
