RV Repair: Furnace Repair, propane appliances, new furnaces

Question
Hi, I have an RV with (2) 30,000 BTU furnaces. Neither one is heating. They are on separate thermostats and I have tried on them on Battery, City Power and Generator. The blower comes on as it should and they never fire. I am full on propane and all other propane appliances work. I have tried the gas valve in both postions on the furnaces. I am about do dismantle (no small job) and see if I can try to track down the problem. Here is the sequence I am going to try. 1) disconnect the propand see if Gas is getting to the connection. 2) Test the voltage going in for 14v +/- 3) Pull the furnace out of the under cabinet space (Ugh!) 4) make sure the sail switch is working 5) Have the IC Boards tested (where do I do this?) and 6) buy new furnaces. Should I do this differently? All help is appreciated.
Rob

Answer
We can rule out the regulator since the stove and other appliances work ok (As long as the flame is blue with only a little yellow), the thermostats are most likely ok since they are seperate units and the fans do come on with them. Before tearing the units completely down try these steps.

1.Make sure the thermocouple is positioned properly in the pilot flame

2.The sail switch senses the air flow. If the air flow is not sufficient then the switch will prevent the furnace from igniting and the fan will run but you will get no heat. Check to see if any heat registers are closed or blocked.

3.A low voltage condition or dirty feilds or blades may cause the fan to run too slow to activate the sail switch.

4.If you have an electronic ignition check to see if the two contacts are touching or are too far apart. They should be about 1/8 apart.

Boards can be tested at most service rv centers. I can look up specific information if you give me the brand year and model furnace and any iformation on the panel or door of the furnace.