Dear Dave,
I just purchased a used unit from a private seller. It is the regular gas model. I am trying to find out the make and model of the furnace. Also, I can see the vent in the rear driver’s side section of the coach but cannot figure out how the access the furnace. It appears to be under the bed or thereabout. Can you shed any light on this. I have tried to the Coachmen site but everything i have found is vague info. —Patrick, 2017 Coachmen Mirada 35BH
Dear Patrick,
From what I can see on the internet, Coachmen used an Atwood/Dometic 30,000 btu furnace. You can see the outside exhaust port on the driver side of the rig. There should be the Dometic name stamped on the exhaust port, and on the thermostat inside.
Access to the furnace
Typically, the access to the module board and burner assembly are from the outside of the rig. First, remove the screws for the exhaust flange and pull it out. Then remove the six screws holding the exterior plate and you should have access to everything. This is an image from etrailer.com of the guts of your furnace.
It does look like the guts of the furnace are located under the bed platform. Trust me, the designers don’t have to work on these so they are usually not in an easy-to-access location.
How the furnace works
There is not much maintenance required, but rather an understanding of the operation. When the thermostat calls for heat, the blower motor starts to exhaust anything in the burner assembly and draws interior air through the return air grate. Airflow is directed over the burner assembly to the interior vents and passes over a sail switch. The airflow must be strong enough to lift the switch that creates a closed circuit, sending voltage to the module board verifying proper operation and open the gas valve. You should then hear the spark ignite and the burner assembly starting.
Troubleshooting
Most troubleshooting you might need should be accessed through the outside opening. There is a reset button that is a high temperature override and an LED light that will blink a code if there is something wrong.
- 1 Flash w/3-second pause – Air Flow/Limit Switch – either low airflow or high temperature
- 2 Flash w/3-second pause – Flame Sense Fault
- 3 Flash w/3-second pause – Ignition Lockout Fault
- Steady On/No Flashing – Internal Control Failure
The only routine maintenance is checking the cover for a tight seal and no moisture penetration and blowing out the exhaust port to make sure there are no spider webs, dust, or mud daubers.
You might also enjoy these posts from Dave
- Why does RV furnace light on second attempt but not first?
- Why does my RV’s furnace only ignite when I lift the sail switch?
- Heat from RV furnace reaches 195 degrees at closest vent. Is this too hot?
- RV furnace vent is 190 degrees. I’m afraid something will catch on fire!
- Why does RV’s furnace run for 20 seconds, then stop?
DAVE HAS ANSWERED MORE THAN 1,000 readers’ maintenance and repair questions. Read a directory here. There is so much to learn!
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
HAVE A QUESTION FOR DAVE?
Send your inquiries to him using the form below.
RVDT2893
Nice to have every piece of documentation on everything installed in the RV.
Even if it’s on the internet, paper is better.