Furnace cycles or wining noise as soon as power is connect to camper

[gwdcamping]

Hello
I have a Montana Highcountry 370br. I winterized it last year. This weekend I wanted to get it ready for the season - so I hooked up power, hooked up the water, as soon as I turned the power on at the circuit panel. MY red light on the circuit board flashes continuously - I had some mudbugs in the exhaust, I cleaned and vacummed that - next I check the sail switch, it looked good, not dirt or dust.

The manual says the flashing lights 1 , 2, 3 and then a pause. Mine doesn't pause. The blower is turning, it is like it starts, stops, starts again at the timing of the flashing which is every second.
Help

[ChuckS]

If I were gonna TS this issue I’d want to isolate a few things… the furnace control module is “seeing a signal” to turn on.. this is sent via the thermostat up to the Zone 1 roof mounted A/C unit control board or gateway..

On the Atwood furnace there are two identical blue wires that are the signal wires receiving signal to turn on or off from thermostat.

I’d remove those two blue wires for the furnace control board connection (mark which went where) because they are same color..

Do this of course with 12 volts DC removed from the RV..

Now turn battery power on and if furnace blower starts up with the blue signal wires removed from its control board this would indicate to me the control board has failed. The blower motor has separate Circuit wiring for it from the Red/Yellow wires going to control module

IF furnace blower motor doesn’t start up then issues is downstream at thermostat, gateway, etc

Image typical Atwood wiring…