Hydro Flame furnace main burner not lighting

I had a late 60's Red Dale truck camper. It was a beautiful unit!
I think I had the same heater and the same issues. You need to clean the flame sensor/thermo-couple end that stick's out into the flame. Use a brass brush or some carburetor cleaner to remove the carbon build up on it. Be sure not to bend it out of position. Excessive carbon insulates the end and keeps it form working. I had to do the same thing to the oven.

By the way, make sure the flame sensor isn't bent down onto the burner. It should be above it and then end should be in the mid part of the flame and when working correctly, will glow as a hot spot in the flame.

I would clean the thermal couple. Make sure it is directly in the flame of the pilot.
You may want to get a replacement.

Well....took the the thermocouple off, cleaned it & reinstalled....still no main burner. So next plan is to disassemble, clean with carburator cleaner before last resort, the gas valve replacement.

Slow down!
Check the thermal couple for operation.
Use a mutlimeter set on millivolts, attach one lead to the tube portion of the thermal couple and the other lead to the center of the thermal couple cable. Heat up the thermal couple probe. You should get 30+ millivolts. Thermal couples are in-expensive. you may want to just replace it.

It could be possible the orifice is clogged. remove it from gas valve and clean with alcohol.

Don't do a gas valve replacement before you check to see if the furnace burner itself is so plugged with wasps nests that it simply can't let the propane out to burn. Wasps love to build nests in these furnaces. I once removed a furnace from a camper and got a coffee can full of wasps nest out of it by shaking and digging around inside the plenum .

P.S. you might find out that you can not get parts for a furnace this old.

The local RV dealer gave me a thermal couple to try. Switched it out & still no main burner. Not sure if it makes any difference or not, but the furnace originally had an aluminum thermal couple & the one they gave me was a copper one to try. Any difference?

I also removed the lower burner access door tonight & inspected the burner box for any obstructions such as wasp nests....didn't find anything other than a few pine needles & cleaned them out. Took off the pilot bracket to try to get to the orifice, but I couldn't get the orifice out, so I will plan on soaking it in alcohol overnight. Thanks again for everybody's input & help....hopefully I can figure it out & it is something other than replacing the entire valve unit.

7lazy77 wrote:
The local RV dealer gave me a thermal couple to try. Switched it out & still no main burner. Not sure if it makes any difference or not, but the furnace originally had an aluminum thermal couple & the one they gave me was a copper one to try. Any difference?

No difference. I'd suggest to buy a new thermocouple and clean the orifice as has been mentioned. You could also lightly tap on the top of the gas valve with a screwdriver handle. The solenoids have been known to stick.

Got it fixed! Just a quick update to let others who encounter a similar problem know what I found. My problem wasn't any obstructions with the furnace burner or a bad thermocouple. It appears that my specific problem was the orifice. I couldn't remove the orifice itself, so I just cleaned the whole pilot bracket containing the orifice in alcohol & even sprayed it with carb cleaner. After I reinstalled, the main burner kicked right on when I turned the dial up.

Thanks for the update! Keep warm!