mine has duo-therm furnaces in it. they didnt work well when i got them and the igniter boards were bad.
they are really not very hard to troubleshoot.
you make sure you are getting power to them. there will be a 12v fuse/breaker somewhere for them as well.
dean is right, when the thermostat turns them on (the thermostat could be bad too), the fan comes on. when the sail switch verifies the fan is turning fast enough and after a certain time (20-30 seconds) then the ignitor will try and light the burner. it will try 3 times usually, then it will stop trying. if it is trying to ignite but do not (you can hear a gentle roar of the burner starting up) then it will stop trying and the fan will run until you turn it off at the thermostat.
then you have to turn the thermostat off and back on to get them to try to refire.
make sure you have propane, the tank is turned on.
some heaters switch the ground and some switch the hot. i replaced the control board with the Fan 50 plus from
http://www.dinosaurelectronics.com/Fan_50_PIN.html.
i converted it from switching the ground to switching 12v so the fan control feature would work. now on mine, after 3 tries of lighting the burner, the fan will shut off. the reason you care about this is that if you were not home in the coach and running the furnace and dry camping, you would run the battery down running a heater that wasnt putting out any heat.
if you have more than one furnace, you can swap parts to troubleshoot them.
be very careful around the propane.
this place has a lot of manual of heaters.
http://bryantrv.com/owners.html
you just have to determine which heater you have.
i will private message you my phone and you are welcome to call me. i have rebuilt all 3 of my furnaces in my coach. no expert, but i was able to get all of mine working great.
have fun!
tom