Forum Discussion

Kenmartin1's avatar
Kenmartin1
Explorer
Oct 28, 2014

Furnace sail switch

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
Class A
  • John_Wayne's avatar
    John_Wayne
    Explorer II
    Oct 28, 2014
    The transfer switch if you have one should be close to where the power cord comes into the MH. the converter could be any where. mine is in the basement a friends was under the refrigerator where you couldn't see it unless you removed a panel.
  • turbojimmy's avatar
    turbojimmy
    Explorer
    Oct 28, 2014
    Kenmartin1 wrote:
    Yc1, you were correct... Upon starting the engine, it's alternator put out enough power for the furnaces to light and put out heat. I realized the coach batteries were run down, and there is a power draw competing for the furnace power.


    Thanks for the follow-up. This is good to know!
  • Kenmartin1's avatar
    Kenmartin1
    Explorer
    Oct 28, 2014
    Yc1, you were correct... Upon starting the engine, it's alternator put out enough power for the furnaces to light and put out heat. I realized the coach batteries were run down, and there is a power draw competing for the furnace power.
  • YC_1's avatar
    YC_1
    Nomad
    Oct 28, 2014
    Kenmartin1 wrote:
    Thanks, I'll try the pb. I have really good batteries.


    You may have great batteries but 12 volts has very little push and a loose connection along the line will drop the voltage quickly. You really need to know the voltage at the furnace with it running so there is a good load on it. Better yet, run them both and test. A poor ground will give you the same low voltage.
  • bsinmich's avatar
    bsinmich
    Explorer
    Oct 28, 2014
    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.
  • YC_1's avatar
    YC_1
    Nomad
    Oct 28, 2014
    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.

About Motorhome Group

38,708 PostsLatest Activity: Mar 05, 2025