Suburban furnace issue

[dee004]

I have an SF30 Suburban furnace. When I turn on the power to the furnace and turn up the thermostat I hear a click coming from the furnace but the blower sometimes does and sometimes doesn't start like normal. At the moment doesn't. The tanks are full and there is propane getting to the furnace because my stove works and it's tee'd off right there 18" from the furnace. I don't have a schematic so I have no clue as to where to test for voltage and what it should be at certain points. Any help would be appreciated. One thing to note would be some mice built a nest in the blower a few years back and I had to remove clean and replace the furnace to clear the jamed blower. The furnace did work for the following two seasons after. Sorry for being so long winded LOL I am mechanically inclined just don't know the ins and outs of heating systems. I'm an Electrician and Lineman by trade as well as a Certified Electronics Tech. I have changed out known faulty gas valves and regulators over the years. Just lost on this one.

[letitsno]

Should have wiring diagram on unit somewhere otherwise find it on line. How old of a unit, in a camper. Most use a very cheap thermostat.

[dee004]

The furnace is a 2006 model. Funny thing is the wife through out the schematic. When I took the furnace out to clear the nest out the schematic came off so I set it aside and well yah know women I looked online but couldn't find my model SF30.

[dee004]

Found a good site with a schematic of the furnace and fairly good trouble shooting guide. Guess I'll give it a whirl. Thanks

http://www.brwholesale.com/itemNotes...ice_Manual.pdf

[letitsno]

Ok looked at a parts break down as I could find a diagram with out paying for it. Thermostat should start blower motor witch also runs combustion blower, than spark should start(might have a delay in board) how they prove that blower is running don't see a pressure switch. Could be a bad board also. Take wires off of thermostat & jumper, tell me what happens.
I own an HVACR company, can fix anything when it's in front of me. Not a parts changer, I love finding problem. Really love them when someone created problem.

[letitsno]

Found it they use a sail switch to prove blower is running. If yours is installed like mine you have to take it out to work on it. Mines much older than yours, but operates much the same. Mine started right away LOL, couldn't help it. I will check back later.

[MikeThompson]

The sail switch is the most common part to fail, but the blower will still run even with a bad sail switch. It's function is to ensure the fan is running before the propane fires. Sounds like there may be a loose wire on the fan since it will run sometimes.

[letitsno]

Ignition won't start until sail switch micro switch has closed proving blower is on. Delay switch for blower could be bad also.

[dee004]

Nothing is accessible without removing the unit from the trailer whats with that?????? I will have to wait til tomorrow now, it's out back in the snow and the sun is going down LOL. After work tomorrow hopefully I can take the furnace out and bring it in and go from there. Guess I'll have to do it on the bench and hook up a temp gas feed. Any suggestions before I do all that. Thanks guy's

[dee004]

One more thing of note: the thermostat is a Dometic which controls the AC as well and as I mentioned earlier it does send some sort of command to the furnace because there is a definite click sound from the furnace when the control is moved up and down.