I have a 96 thor residency 36' motorhome that has been sitting for a few years. Has front and rear furnaces, ignition style atwoods. Upon starting, both furnaces fan's run strong, but wouldn't light. I bypassed the sail switch and both furnaces operate properly. I removed a sail switch and tested it for continuity, and it works! My fans seem to be blowing strong out of all floor vents... Do these switches get stiff or stuck when old???One other question: I can find a power transfer switch, or converter, if anyone knows where they may be hidden. Thanks, Ken

Moved from Forum Technical Support

I've had sail switch's get sticky, sometimes a little PB will loosen them up.

They may need a little PB as suggested and some exercise. The heaters require sufficient voltage for the fan motors to run fast enough so I would measure the DC voltage at the heater. Since both have failed the common thing is DC voltage.

Thanks, I'll try the pb. I have really good batteries.

Try running one furnace at a time. That should give a little higher voltage for the fan. If that helps you have a battery voltage problem. You could also measure battery voltage when the furnace is running.

Furnace sail switch | Good Sam Community

YC_1
Nomad
Oct 28, 2014
Do you have an Inverter?
Kenmartin1
Explorer
Oct 29, 2014
One in the front cabinet, maybe just to run the tv.
YC_1
Nomad
Oct 29, 2014
Four volts in an hour would be a massive draw. I highly suspect you have sick batteries.
Kenmartin1
Explorer
Nov 06, 2014
I tracked down the power draw by placing the meter between the battery ground wire and its post, to measure the draw. Then followed power wires back from the battery. Everywhere power split, I removed each wire until the power draw was gone. I have a box of relays on my engine compartment, and by disconnecting one wire there, the power draw is gone. Now I have to figure out where that wire goes...however, everything on the coach seems to work! Ken
Coyote74
Explorer
Nov 06, 2014
What is pb?
Jagtech
Explorer
Nov 07, 2014
Kenmartin1 wrote:
I have a 96 thor residency 36' motorhome that has been sitting for a few years. Has front and rear furnaces, ignition style atwoods. Upon starting, both furnaces fan's run strong, but wouldn't light. I bypassed the sail switch and both furnaces operate properly. I removed a sail switch and tested it for continuity, and it works! My fans seem to be blowing strong out of all floor vents... Do these switches get stiff or stuck when old???

Thanks, Ken

Sail switches are basically a sensitive microswitch. They do become "flakey" or intermittent before failing completely. A continuity test may indicate they are good, but that isn't the best test. The contacts inside the switch become corroded or dirty, and when operated by hand they will often test good. Using a DMM on a low-ohms scale, you will likely see the resistance of the switch bouncing around from a few ohms to several hundred ohms. If the furnace works fine with the switch bypassed, then replace it.
jhilley
Explorer
Nov 07, 2014
Coyote74 wrote:
What is pb?

It is PB Blaster
Dutch_12078
Explorer II
Nov 07, 2014
I've repaired several furnace issues over the years where the failure was caused by kitchen grease buildup on the sail switch blade. The sticky grease and dirt buildup made the blade enough heavier that the sail switch either didn't operate at all, or only operated when the fan spun up higher at peak voltage from the converter. A common complaint in that situation was that the furnace worked okay on shorepower, but not on battery power.
Coyote74
Explorer
Nov 07, 2014
Thanks for the answer to my question on pb! jhilley. I thought about electrical contact cleaner.
Never heard of pb.

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