Sail Switch on the Furnace

[howson]

I've read the term numerous times but didn't know what it looked like or why it was called a "Sail Switch". It's a mystery no more.

What the sail switch does it ensure there's airflow before the furnace fires up the propane. The switch has an arm that reaches up into the furnace's blower. When the blower spins the air pushes against the switch arm. When the switch engages the furnace knows it is OK to fire up the propane. So if this switch goes bad the heater will not turn on the propane, but you'll hear the blower spin.

[colan]

In addition to a sail switch not closing the other common problem is the sail switch sticking closed.

When the thermostat calls for heat the first thing the control board does is check for a closed sail switch. If the board finds the sail switch closed before starting the fan nothing happens. Sometimes rap with the knuckles on the motor case or just removing the furnace cover will unstick the sail switch. If this happens would suggest not thinking the problem is solved. If the sail switch sticks once it will stick again.

A way to confirm a switch that is stuck closed is to remove one of the wires to the switch. Removing a wire from the sail switch simulates an open switch. Once the fan starts reconnect the wire removed from the sail switch. At this point the furnace should progress through the purge cycle and light confirming a stuck or sticking switch.

[Yoda]

howson
Is that part replaceable? Looks like its riveted to the blower housing?
Thanks Keith

[howson]

howson
Is that part replaceable? Looks like its riveted to the blower housing?
Thanks Keith

Country Campers -- can you take a look?

[Country Campers]

They are actually philips head. The spare furnace I have is actually quite different than the one we have pictures of here. Will do some more investigating.

Brian

[tesarsue]

Thank you, everyone!! I appreciate your assistance. We have the trailer stored. Once we camp this weekend. I will get you more information.

[DonWesternMA]

Please make sure you do...too many of these problems never include the solution...

[Scott'n'Wendy]

howson
Is that part replaceable? Looks like its riveted to the blower housing?
Thanks Keith

Those are screws passing through the micro switch to the blower housing. Remove them and the switch is in your hand.

A nice thing about functioning micro switches is they make a very tactile and audible 'click' when they activate.

[Scott'n'Wendy]

This not an identical micro switch (not a sail switch off a furnace) but it shows the mounting holes.