Sail Switch

[Videocrafters]

Start up the furnace and the fan spins but does not spark for the gas. Removed the sail switch and found a piece of lint on it. Cleaned off the lint and checked the switch with an ohm meter. Switch works. Put the old sail switch back in. Furnace does not ignite. Remove the old sail switch and replace with a new one. Still no luck.
Now what?

[davidmurphy02]

When the furnace fails to ignite, the LED on the circuit board should flash - one, two, three, or four flashes - and repeat several times. There should be a sticker on the blower motor case below the circuit board that shows the error codes to give an indication of the problem depending on the number of flashes, try checking that out.

When you turn the furnace on, standing outside with the cover off do you hear a repeated electronic clicking that indicates the spark igniter is working? If the sail switch is OK, the igniter should try to fire several times and make a series of loud rapid clicks.

If the blower motor comes on but the furnace does not, how long does it run before shutting off? If it shuts off after about 30 seconds, that usually means the sail switch did not work. If the sail switch is OK, and the blower motor shuts off after about 60 seconds, that usually indicates a problem in the ignition process, could be either the circuit board or the igniter.

[Videocrafters]

Thanks David for the detailed response.
The fan shuts off after 30 seconds.
The 1 blink code says
AIR FLOW LIMIT FAULT.
so sounds like the sail switch is not working properly?
It checks out on the ohm meter so it is working. Not sure if I could install it incorrectly. Seems straight forward..
Any thoughts?

[MVA]

Have you checked the other item "limit fault"? There is a high temp switch in series with the sail switch which should be NC (normally closed). They are ubiquitous on heating devices (laundry dryers, furnaces, ....).

Per David's question, I assume you do not hear any clicking or smell propane?

[davidmurphy02]

Originally Posted by Videocrafters

Thanks David for the detailed response.
The fan shuts off after 30 seconds.
The 1 blink code says
AIR FLOW LIMIT FAULT.
so sounds like the sail switch is not working properly?
It checks out on the ohm meter so it is working. Not sure if I could install it incorrectly. Seems straight forward..
Any thoughts?

Based on all the problems people have had with these sail switches, I think it is still possible that it could not work properly even if it tests out electrically when uninstalled, would certainly be worth getting another since they are inexpensive and in any case good to have a spare on hand.

A couple of other lower probability possibilities with that error code - the sail switch could be OK but the blower motor is not turning fast enough to move the sail and activate it. Are you on shore power now or batteries? If you are on battery power and the battery voltage is a little low the blower motor may not turn as fast, and apparently these furnaces have very little margin between "OK airflow" and "Not enough airflow".

There is also a high limit switch designed to shut off the furnace if for any reason it gets too hot. That's the "limit" in your error code. Pretty rare for this to go out, but certainly not impossible. It's round, the size of a dime, and has two wires connecting to it. In this photo it is just above the burner exhaust tube. If you can get multimeter probes back in there to test it, you should get continuity across those two terminals. If an overheated situation caused the switch to fail something inside it would melt and break the continuity. It could probably also fail just on its own - anything can break.

[Videocrafters]

Ok, I have two sail switches with me along with the original and the two new ones all check out on the ohm meter as did the original. I have installed both new switches and none of them work. So as an experiment I pulled both wires off the sail switch and shorted them together and the furnace started right up with no issues. So the problem must be the sail switch (all 3 of them).
I don’t know what else to do.

[MVA]

I would double check the high temp switch. Probably not the problem but worth the check. I concur with David's comment that the fan may not be turning fast enough to close the sail switch. This situation occurred on a myrvworks video. If the fan turning freely?

[davidmurphy02]

If shorting the wires got the furnace to ignite then that rules out the high limit switch - if it was bad it would still not ignite. The odds of multiple bad sail switches seem pretty low. So the possibility is still out there of a low air flow problem, either due to low voltage or possibly a problem in the blower motor. Without enough air flow to activate it, a perfectly good sail switch would not give the OK signal to the circuit board.

It is not - or at least should not - be possible to just bypass the sail switch by shorting the two wires together. The circuit board needs to receive an "open" signal from the sail switch first, then it turns on the blower motor, then looks for a "closed" signal from the sail switch indicating enough air flow to move the sail and close the switch, and then it activates the igniter and burner. Since it needs to read both open and closed positions every time the furnace cycles, just joining the wires and bypassing the switch wouldn't work as an ongoing fix. By shorting the sail switch wires during the initial process you sent that "closed" signal to the circuit board and got it to continue with the ignition process. But if the airflow from the blower motor is not quite adequate, this is a less than completely safe situation - and is the sail switch's reason for existence.

[hugh]

There's another thread on here somewhere, but one of the common problems with the sail switch is that the metal vane (paddle) is a bit too long for the blower cavity, so it gets stuck. As far as I can tell, it's actually a design flaw with the furnace.

On mine, I just took a pair of metal snips and cut off a half of an inch of the end of the vane, and I've had no problems since then.

[Videocrafters]

Well my voltage is 12.4. Foggy day on Washington west coast and deep canopy of trees so solar is having trouble keeping up. Although 12.4 does not seem that low maybe it could be an issue. Tomorrow we leave so when I connect up the truck I will
have plenty of volts so I can see if that helps.

[brroberts]

Mine acts up at 12.4 volts. If I’m not over 12.6, my furnace is not very reliable.

[Videocrafters]

Ok, now I have 13.7 volts.
I removed and reinstalled the sail switch for the 4th time.
Here is what happens now.
1. Fan starts
2. Ignition sparks.
3. Propane ignites for a second but does not stay lit.
Then it keeps repeating.
No blinking led light

Any ideas?

[Rockhead]

We had the same issues on our 2018 21. Changed out switch had proper voltage. No joy. We then changed out the propane regular and have t had any issues since. Just throwing this out there

[davidmurphy02]

Originally Posted by Videocrafters

Ok, now I have 13.7 volts.
I removed and reinstalled the sail switch for the 4th time.
Here is what happens now.
1. Fan starts
2. Ignition sparks.
3. Propane ignites for a second but does not stay lit.
Then it keeps repeating.
No blinking led light

Any ideas?

I had similar problems a couple of years ago that drove me nuts trying to figure out. Replaced the sail switch, circuit board, modified the air intake inside for better airflow, all to no avail - sporadic ignition that would work once in a while but continued to fail regularly.

I finally replaced the gas valve and the igniter, furnace immediately fired right up on the first click of ignition and has worked flawlessly ever since. I'll never know for sure whether it was the gas valve or the igniter, but the valve, burner and igniter are all one unit that has to be removed to replace any of those items I replaced them both.

[Videocrafters]

Well,or,regulator,seems to be working fine for the frige and stove and hot water heater. So I don’t know about that. Maybe….

[Videocrafters]

Is that a difficult job? Does the whole furnace need to be taken out to do it?

[davidmurphy02]

Originally Posted by Videocrafters

Well,or,regulator,seems to be working fine for the frige and stove and hot water heater. So I don’t know about that. Maybe….

It's not a regulator, it's the valve that turns the gas flow on and off. It gets the proper pressure from the main regulator at the propane tanks.

[davidmurphy02]

Originally Posted by Videocrafters

Is that a difficult job? Does the whole furnace need to be taken out to do it?

It can be removed from outside. Not too bad, a matter of disconnecting the gas line from the top of the valve (turn gas off first, of course) and several screws on the back wall of the exterior compartment to remove, you just need a long extension for the driver bit to access those screws.

Here's a thread from earlier that goes into more detail: https://www.escapeforum.org/forums/f...ing-20805.html

[Videocrafters]

Thanks David you have been very helpful

[Rockhead]

Originally Posted by Videocrafters

Well,or,regulator,seems to be working fine for the frige and stove and hot water heater. So I don’t know about that. Maybe….

Same here everything else worked fine but the heater. When we changed out the regulator heater started working fine and since then. Nothing else was replaced