|
My furnace repair
Have a 1981 Winnebago Brave 26RH Four Season Motorhome and passing it onto our Son for his lake lot.
It has a Coleman furnace, model 4334-749.
A few years after purchasing the RV (second owner) the furnace gave us grief every time we tried to start it.
As old as this furnace is it still has the basic principles of what we have now.
This furnace is not serviceable in place. Removal was needed and was surprisingly easy to do although required breaking the exterior vent seal.
I took lots of pics on every step for easy install/assembly.
Found before removing:
- Fuse was good.
- Thermostat metered fine and was set to correct amps.
- Sufficient battery power.
- Sufficient propane level.
- Gas pressure was low.
Found at 8 inches Water Column on gauge at furthest appliance (fridge). This furnace requires minimal constant 11 inches (0.397 PSI). Increased to 12 inches W.C.
Thought this was the problem but not (no other appliances running on test).
Found after removing:
- Bird tried building a nest in the exhaust (not noticeable until vent was removed).
Good thing it did not fire up, pulled all the fine twigs out.
- Sail switch tested good with meter.
- Overload switch tested good with meter.
- Igniter wire was loose on circuit board and connection broke when touched.
Installed new connector and tightened.
- Igniter tip and sensor in flame box were coated.
Removed and carefully cleaned with fine sandpaper.
- Igniter tip gap seemed too much.
Slightly bent tips together taking sensor position in consideration (no specs in the manual for this).
- Sail switch connection at relay was almost touching ground.
Bent connectors away from each other and placed an isolator (tape).
- Burner was 80% plugged.
Removed and cleaned internal and external with extended wire brush on drill, pipe cleaners and air.
- Burner box was fouled with what looked like rust and carbon.
Tipped, turned, tapped and blew with air until residue stopped coming out of box.
All cleaning required air movement and mask.
- Gas valve internals had sticky residue.
Disassembled the whole unit to clean with carb cleaner and air. Care was needed not to damage gaskets or diaphragm.
After furnace install I opened the propane with power off to furnace. Used my nose and a handheld gas/propane leak detector with flexible head for leak checking up to the valve (detectors are cheap on Amazon but test before using. I test on our propane BBQ without ignition, quickly reads high).
When the furnace started I checked the whole system because on fire up the gas valve opens and could produce a leak in the valve body or downstream.
On this furnace spraying a leak detector around the valve could damage the control board and not easy checking the backside of the valve. Flexible head on the leak detector allowed me to get into tight spaces.
No leaks found.
The furnace now fires up on first command.
Beside sealing the exterior vent after I'm Kicking myself for not spending an hour on these repairs years ago.
|
from a Toronto Canuck
Linear Mode
