Dometic furnace won't kick on

[winnielife]

I have a 2022 2801bhs, not sure which model furnace I have since the manuals are in the TT. It got quite cold on the last camp and the furnace wouldn't kick on when I switch the thermostat to furnace and set the desired temp higher. The fan didn't even turn on, I'm not even sure where the fan is. Looks like the air intact is inside the closet by the door. I took the panel off on the outside and all the wires seemed to be connected, hit the reset button a few times but no help. Any idea what could be the issue before I take in for service?

Also, I couldn't get the front Dometic a/c to generate heat. I turned the dials to various settings, thought I turned the temp to heat but just blew cold air. Any idea what I'm doing wrong there?

[powercat_ras]

As a 2022 it should be a spark ignition furnace.

There should be a 10 amp fuse dedicated to feeding the furnace power.

If that fuse is good and the thermostat calls for heat it puts 12 volts on a thermostat output wire that runs to the furnace connected to an input on the furnace's control board.

The control board should power up the blower motor, you would normally be able to hear that.

The control board looks for confirmation that the blower is spinning by looking for a signal from a sensor called a sail switch that operates from air blowing out over it from the blower wheel.

If that is satisfied, then turns on propane to the burner and starts sparking. It will try this about 3 times or until it gets a signal from a flame sensor that operates if it sees heat from the burner.

If it tries 3 times and never sees the heat signal then the furnace will go into "lockout" and wait some amount of time before trying again, to keep from creating a fire hazard from unburned propane.

The lockout time is typically 1 hour. You can reset from lockout by pulling and reinserting the furnace fuse.

Bottom line, even with propane completely shut off you should be able to set the thermostat to call for heat and get confirmation the furnace has 12 volt power and that the blower will run, ONCE before it goes into 1 hour lockout. You might even be able to hear it try to spark if you are outside by the furnace outside air vents depending on how loud the noise from the blower is.

[winnielife]

Good info randy, thanks. Where is the blower on a 2801bhs? Where is this 10a fuse, fuse box in the kitchen?

I wonder if I can try these things with the rv at the lot not plugged into anything.

[Morich]

I might think a bit different line to check but need to verify some things.
Is the same thermostat used for both the rooftop heat strip and the furnace?
That might make the thermostat and wiring as a common point for two items to fail.
Possibly just a matter of the thermostat not getting the 12 volt power to operate or the thermostat itself may have failed.

The thermostat is just a switch but it operates by temperature rather than us moving something, so if that switch/ thermostat is not working, the furnace doesn't get any signal to do anything nor does the rooftop heatstrip. Possibly not the AC either but when cold you may not have checked that!

We don't get the good wiring info on trailers but a way to go would be to check the thermostat for a brand and model nmber, then go online to find the info on where the 12 volt connects to it.
With that info one can then check for wiring or power problems.

This is assuming that it is a 12 Volt thermostat and not one using batteries, etc onboard?? New trailer and nobody has changed out the thermostat, right!

[powercat_ras]

Originally Posted by winnielife

Good info randy, thanks. Where is the blower on a 2801bhs? Where is this 10a fuse, fuse box in the kitchen?

I wonder if I can try these things with the rv at the lot not plugged into anything.

The blower is INSIDE the furnace. The furnace will be inside somewhere you can get it's location by locating the outside furnace combustion air inlet/outlet. I see it under the fridge on a lot of small TTs.

The fuse will be one of many in a 12 volt fuse box, I see a combined 12V fuses / 120V breakers in one box in many TTs You might luck out and even be able to have fuses labeled and labels readable depending on who installed the box in your particular unit.

If your unit has a thermostat with LCD temp display if the LCD is showing a temp then the thermostat has 12 volt power and ground. Generally the thermostat will have a 4 position switch if your RV has a roof top unit that can heat as well as cool. The switch will be something like : AC - OFF - GAS HEAT - ELEC HEAT

[Ray,IN]

First try out the KISS principle. Remove 'stat from wall, unplug/reattach terminals (both ends of wire) several times to clean them of corrosion. Leave positive wire unplugged for 30 minutes then reattach.
Still doesn't work, the only thing you lost is time. Now you get to begin spending money.