Sail switch power

[Mark28RYR]

Hello! I have a 2020 Keystone Cougar. Having issues with the furnace intermittently working and then not working. Blower will start, then no ignition and it will cut off after about 20 seconds or so. It appears that the sail switch isn’t always receiving power (checked this with a meter). The furnace is controlled by the In-Command display. Would anyone be familiar where the wire that provides power to the sail switch goes to? I believe it is one of the two blue thermostat wires. One (think it is negative) is capped off. The positive is what connects to the sail switch. I’ve swapped sail switches a couple times and even though I’ve had issues with the Amazon ones the original still operates correctly when tested with a multimeter. Thoughts? Thank you.

[dutchmensport]

The sail switch is activated by the force of the wind blowing over it. It almost sounds like the fan speed is changing. When the fan slows down, it causes the sail switch to shut off. When it picks up again, it makes contact like it's suppose to. The furnace fan is run off 12 volt DC house battery. Are your batteries charged fully? If not, the variations in fan speed could be caused because the converter is not spitting out a steady 12 volt DC charge and if the battery is low or not charged, the fan is running from the converter and the charge from the converter is pulsating.

[Mark28RYR]

Originally Posted by dutchmensport

The sail switch is activated by the force of the wind blowing over it. It almost sounds like the fan speed is changing. When the fan slows down, it causes the sail switch to shut off. When it picks up again, it makes contact like it's suppose to. The furnace fan is run off 12 volt DC house battery. Are your batteries charged fully? If not, the variations in fan speed could be caused because the converter is not spitting out a steady 12 volt DC charge and if the battery is low or not charged, the fan is running from the converter and the charge from the converter is pulsating.

Right, I understand how the switch works but power sits at one side of that switch until it is activated by the fan. Where is it’s power source.

[chuckster57]

Originally Posted by Mark28RYR

Right, I understand how the switch works but power sits at one side of that switch until it is activated by the fan. Where is it’s power source.

From the control board. 12VDC activates the furnace ignition control board. 12VDC is sent to the limit switch, then the sail switch, and then back to the board. If all is good, 12VDC is sent to the gas valve and igniter.

[Mark28RYR]

Originally Posted by chuckster57

From the control board. 12VDC activates the furnace ignition control board. 12VDC is sent to the limit switch, then the sail switch, and then back to the board. If all is good, 12VDC is sent to the gas valve and igniter.

Ok, so does the thermostat get power from the control board too even being it’s a In Command system? Looking at this diagram there’s two wires on one side of the sail switch. One from the control board and the other says thermostat. I tried attaching a photo of the schematic.

[ChuckS]

The Zone 1 AC gateway is what sends signal to furnace control board to operate furnace

The FURNACE control board gets its 12 vdc directly from an ATC fuse on your inside power panel.

The roof AC gateways get their 12 vdc from another source

** if Zone 1 roof AC gateway has no 12 vdc you will see an F — for temp display

[ChuckS]

Also on your case with In Command controlling the Furance both blue wires run all the way to,the roof to Zone 1 AC gateway ..

There are wire caps at the furnace on the four wires . The two blue ones connect to different color wires that run up to that Zone 1 roof AC gateway to complete the circuit to tell furance to run or to turn off

[Mark28RYR]

Originally Posted by ChuckS

Also on your case with In Command controlling the Furance both blue wires run all the way to,the roof to Zone 1 AC gateway ..

There are wire caps at the furnace on the four wires . The two blue ones connect to different color wires that run up to that Zone 1 roof AC gateway to complete the circuit to tell furance to run or to turn off

My blue wire labeled Thermostat + is just capped at the furnace. The second blue wire just labeled Thermostat is connected.

[jsb5717]

Could it be as simple as a faulty or dirty sail switch? Have you pulled the switch to check? A faulty or internally dirty switch should just be replaced. But I've had a little bit of lint impede the function of the sail switch. A simple cleaning had the furnace back up and running normally.

You can also jump the wires at the sail switch...basically bypassing it. If the furnace runs normally then there's an issue with the sail switch. Don't leave the jumper on the switch, it's just a test. But it should tell you whether to look at the switch or someplace else.

[Mark28RYR]

Originally Posted by jsb5717

Could it be as simple as a faulty or dirty sail switch? Have you pulled the switch to check? A faulty or internally dirty switch should just be replaced. But I've had a little bit of lint impede the function of the sail switch. A simple cleaning had the furnace back up and running normally.

You can also jump the wires at the sail switch...basically bypassing it. If the furnace runs normally then there's an issue with the sail switch. Don't leave the jumper on the switch, it's just a test. But it should tell you whether to look at the switch or someplace else.

Unfortunately no, it’s more than that. I don’t even have power to the sail switch at the moment. It ran fine all day today and cut off and won’t ignite anymore as of 2 hours ago.

[jsb5717]

It won't ignite if the sail switch is failing. That's why it's worth bypassing that switch to see if the furnace will try to ignite. If the fan is spinning up when the thermostat is calling for heat then the thermostat is working and so is the relay in the AC. That also means there is power to the furnace so that's not the issue.

If the fan spins up but there's no ignition then I would look at 3 possibilities. Sail Switch, Limit Switch, Control board. The Limit Switch can fail but it doesn't very often. The Sail Switch is the easiest to quickly test by jumping (bypassing) it. FWIW, you can also jumper (bypass) the Limit Switch just as easily just to eliminate it as a potential issue.

[Mark28RYR]

Originally Posted by jsb5717

It won't ignite if the sail switch is failing. That's why it's worth bypassing that switch to see if the furnace will try to ignite. If the fan is spinning up when the thermostat is calling for heat then the thermostat is working and so is the relay in the AC. That also means there is power to the furnace so that's not the issue.

If the fan spins up but there's no ignition then I would look at 3 possibilities. Sail Switch, Limit Switch, Control board. The Limit Switch can fail but it doesn't very often. The Sail Switch is the easiest to quickly test by jumping (bypassing) it. FWIW, you can also jumper (bypass) the Limit Switch just as easily just to eliminate it as a potential issue.

What if my battery is bad? Even though I’m connected to shore power I’m seeing mentions of the furnace not operating correctly if the battery is weak. When the blower starts I have no power to either side of the sail switch so it’s definitely not that.

[chuckster57]

Have you tested the limit switch?

[Mark28RYR]

I replaced that the other day. I’m getting 12v at the sail switch for just a second and then it goes away. It also looks like the limit switch comes after the sail switch in that circuit.

[jsb5717]

I would ignore that for now. If you are connected to shore power your converter will run your 12 volt systems. If your batteries are weak I would replace them but the furnace should still run normally on shore power and a properly functioning converter.

Don't worry at this point about how much voltage you're reading at the sail switch. You should have the full 12 volts to the main board, which runs all of the furnace systems (you should be able to test that with your MM at the control board pins. Your schematic shows them.)

Just jump the sail switch and see what happens. If it doesn't try to ignite then I would assume a faulty control board.

[Mark28RYR]

Originally Posted by jsb5717

I would ignore that for now. If you are connected to shore power your converter will run your 12 volt systems. If your batteries are weak I would replace them but the furnace should still run normally on shore power and a properly functioning converter.

Don't worry at this point about how much voltage you're reading at the sail switch. You should have the full 12 volts to the main board, which runs all of the furnace systems (you should be able to test that with your MM at the control board pins. Your schematic shows them.)

Just jump the sail switch and see what happens. If it doesn't try to ignite then I would assume a faulty control board.

When I bypass the sail switch the blower fan wouldn’t even come on. As soon as I removed the bypass jumper it started.

[LHaven]

I don't know if anyone has answered your original question in a clear-enough fashion.

Four wires go to the furnace. Two of the are +12V and ground. That is the only power to the whole unit.

The other two are usually blue, and go to the thermostat (sometimes not directly). They are nothing but switch leads. When the thermostat wants heat it shorts them together, otherwise it leaves them open. The only power feed in the whole system is that first 12V wire.

The sail switch is nothing but a switch also. When it is "sailing," it shorts its two leads, informing the control board that the fan is operational and it is safe to start flame. When it doesn't sail, it doesn't conduct power to the board pin that indicates successful fan operation.

The sequence of fan start for 20 seconds or so, no "snap, snap, snap" from the igniter, and fan stopping is the classic sequence indicating sail switch malfunction.

If you are shorting the sail switch leads at the switch (without disconnecting them at the far ends) and the blower won't even start, I can't imagine how that could be.

[JBM3M]

I don't know for sure, but I had a new sail switch that wouldn't allow ignite, so I slightly bent the arm so it would catch air better. This week is first time it has been used since repair and (fortunately at 37 degrees) it is working fine.

[ChuckS]

Originally Posted by Mark28RYR

My blue wire labeled Thermostat + is just capped at the furnace. The second blue wire just labeled Thermostat is connected.

Then the wire that should be to that capped wire is missing.. There must be a wire connected to each of the blue wires going to the furnace...

Those two wires lead directly to the Zone 1 AC gateway control.. Without that other blue wire connected I cannot understand how the furnace control board is gonna ever get a SIGNAL to turn ON]

[ChuckS]

Originally Posted by Mark28RYR

When I bypass the sail switch the blower fan wouldn’t even come on. As soon as I removed the bypass jumper it started.

** And the blower motor never will spin up with the sail switch bypassed.. The Control board looks for an OPEN in the circuit upon initial demand for heat.

Once the board determines the sail switch is OPEN then the blower will get power and run.. then the sail switch circuit is completed when paddle arm moves to complete circuit...