Mine wouldn’t light one trip. It was pretty chilly or cold but especially wet out. After getting some dry heat via other source it worked. Not sure it still works though, maybe I’ll try it out today. Been using electric heater.
Got tired of typing this so saved it as a text file....
When the T-Stat calls for heat the control board starts the blower (1)
The blower blows closing the sail switch (2)
The control board then opens the gas valve (3) and begins sparking (4.1)
Gas Flows (5) And ignitets (4.2)
The flame heats the flame sensor (5)
The flame sensor sends .480 volts to the control board (6)
which then detects the .480 and continues operation (*)
When the T-stat says "Enough already" (RV is now warm)
The control board shuts off the gas flow (*)
and then turns off the blower after a cool down (*)
*: At nearly every step the control board is involved. IF IT IS BAD, things will not work.. I recommend replacement boards from Dinosaur boards.. When Mine went out the Dino board was less than half the price and when opened the box the quality of construction and workmanship, and then design was very clear to my trained eyes.
1: No 12 volt to furnace, blower motor shot
2: Low 12 volt, air ducts clogged, blower "obstructed" bad sail switch
3: Bad solenoid, Clogged Gas Jet
4: .1: Bad ignition circuit (high voltage) on control board. .2: Points too wide (Very common it seems)
5: These do not often fail but they can
5: Bad connection, NOTE:
5 and * Bad wire.
* applies to all steps by the way So does bad wire/connection.
Can you hear the igniter trying to light. It will make a clicking sound. You may just have air in the lines . Try lighting the stove to purge the air pockets. Try lighting the heater again with the stove lit. Also could be a bad propane regulator.
I work in an Rv Shop: 90% of the time if the blower comes on but there is not tick, tick tick following it , it is the sail switch...easy to replace..may have to pull the furnace depending on how the factory installed the furnace.
If fan comes on, and there is an audible loud click once then the gas valve is opening which indicates the sail switch and control board are functioning properly. (Either the chamber is blocked(wasp nest,dirt dobbers, or ignitor are inop)
Hope its the 1st, cheap and easy to replace. Good Luck