Sail switch adjustment

Question

While camping at 9,000+ feet we had difficulty running the furnance. It would turn on, run the fan a bit, and then shut off. It never tried to light and it worked fine at lower altitudes. All of this suggests to me that the sail switch needs to be adjusted. Is that possible? Anybody have some experience or advice?

The furnace is a suburban.

dougrainer · Answer

The sail switch is just a paddle on a metal stem. The ONLY thing that will cause a sail switch to not close would be inadequate Blower Fan speed. What your problem is, is the Altitude and how it relates to LP vaporization. Start the furnace, go outside at the outside vent. Within 30 seconds you should hear the Electric Piezo ignitor start clicking. IF you hear this, the Sail switch is closing. Also, if on BATTERY power only, then the battery may not be supplying enough DC current(lower than 12 volts) to turn the Fan motor to the correct RPM's to close the sail switch. Doug

huntindog · Answer

There is no adjustment for the Suburban sail switch.. And mine only last about 3 years.. Granted, My furnace gets a lot more use than normal, but still they go bad a lot. They will often work intermitantly when they start to fail.
Fortunantly they are cheap and not terribly hard to replace. I paid about 8.00 apiece for mine. I know carry a spare.

time2roll · Answer

What was your battery voltage at the fuse panel?

wolfe10 · Answer

Indeed, you have already received the most likely answers.

But certainly verify that all vents are open, return is clear, no ducts crushed. Any of these will also reduce air flow and can affect sail switch.

scclockdr · Answer

One additional cause for high altitude sail switch issues might be the breakage of a few to several squirrel cage vanes. Ours was plastic and we were having intermittent issues with the furnace lightning. Finally enough vanes failed we smelled hot plastic followed by a grinding and permanent shutdown, as half of the cage completely failed. Replaced the cage and removed all the broken vanes and all was well again.
While trying to solve the intermittent issue I called Suburban and they shipped a sail switch gratis.

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Sail switch adjustment

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