No heat!

[M109pilot]

Currently set up north of memphis. Recently my heat started to have intermittent issues. The other morning, I woke up to 43 degrees in my camper. I did disconnect my tanks thinking my the were empty but they are not. I hooked them up again and that same night the heat worked again. I heard it come on about 3 times. Now it's not working at all. I did find this super secret switch mentioned here but that didn't do the trick. This morning it was 48 inside with the temp outside behind about 35. I don't think the heat came on last night because I didn't hear a thing. In the 8 hours that I was asleep I didn't rub any electric heat. Should the inside temp gotten colder?

Thoughts?

Jason

[RogerR]

Since it is intermittent I would consider looking at the sail switch as the culprit but not ignore some other causes.

Check the thermostat, mechanical ones can get dust in them, loose wires or just fail.
Check for loose or poor connections to the 12 volt system to the fan and board.

Check the outside and inside vents for blockages to air flow for the burner and blower. If your blower is partially blocked the sail switch won't detect enough flow to permit the burner to run.

After those checks then it is the notorious "sail switch" failure mentioned in dozens of posts.

PS. why not use an electric heater if you are plugged into electricity?

[Marine71-76]

Check your regulator...that happened to us last year. And thank goodness for the electric fireplace & small heaters.

[M109pilot]

Thanks, guys.

I don't feel comfortable using electric heaters at night while I'm sleeping. Maybe I'm being paranoid?
I also like to have the furnace running at night just to keep some heat moving through the floor. I don't want to risk my pipes freezing. I leave the furnace on about 55 at night. Again, maybe I'm being paranoid.

I'll look into the exhaust to see if there is anything blocking it. As for the other vents, they aren't easy to get to. My unit is only accessible through the basement. I have a 2016 355mbqs,for those who may be wondering.

Jason

[M109pilot]

But the stove works?

[JimD]

Here is an excerpt from a troubleshooting document I am putting together.

Furnace Troubleshooting Hints

The furnace is a 12 volt device, not including the propane section. To operate it only needs a 12 volt power source plus a 12 volt signal from the thermostat.

The typical sequence of operation is for the thermostat to send the 12 volt turn on signal to the furnace. This should cause the blower motor to turn on. The blower air stream activates what is known as a “sail switch” which is a little piece of metal or plastic that moves and activates a switch when sufficient air flow is present. If no or insufficient air flow is not detected for 30 seconds, the unit will time out in an error condition and shut down.

Provided the sail switch makes contact, the next thing to happen is the control board will energize the gas valve and initiate a high voltage spark for ignition for 7 seconds. If the flame is not sensed within the 7 seconds the control board will repeat the sequence twice more. If all 3 attempts at ignition fail, the unit will enter a lockdown mode.

Common failures:

1. Blower operates but insufficient air flow due to blockage in the air chamber from wasp nests or other intrusions. Clean out air chamber.

2. Sail stuck causing sail switch to not actuate. Free up sail (WD40 maybe).

3. Bad sail switch. Replace switch.

To make troubleshooting easier, download the service manual for your model. There may be a troubleshooting flowchart that you can follow.

[Jagiven]

Sail switch seems to be the most common issue. Usually you have to pull the furnace to gain access . One symptom of a faulty sail switch, the blower will run for about 30 seconds, than the furnace shuts down. It will try about 3 times than shutdown until you restart/set the furnace.

At night, I place an electric heater on the stove top, with the cord on the counter so the dog or a person cannot snag it. Now days all electric heaters have tip sensors on them too.

[Rustynuts]

If the blower comes on for a short time and then shut down it is most likely the sail switch. Sometimes cleaning will help fix it, sometimes not.


If the blower comes on and then the burner tries to fire but then shuts down it is most likely the high temperature switch and the furnace thinks its to hot and shuts down.


These are the two most common failures on a gas furnace. What altitude are you at? some people have issues at altitudes over 5000ft while others dont.

[M109pilot]

I don't even think the blower comes on. I wild hear that, I think.

[TaftCoach]

Originally Posted by JimD

Here is an excerpt from a troubleshooting document I am putting together.

Furnace Troubleshooting Hints

The furnace is a 12 volt device, not including the propane section. To operate it only needs a 12 volt power source plus a 12 volt signal from the thermostat.

The typical sequence of operation is for the thermostat to send the 12 volt turn on signal to the furnace. This should cause the blower motor to turn on. The blower air stream activates what is known as a “sail switch” which is a little piece of metal or plastic that moves and activates a switch when sufficient air flow is present. If no or insufficient air flow is not detected for 30 seconds, the unit will time out in an error condition and shut down.

Provided the sail switch makes contact, the next thing to happen is the control board will energize the gas valve and initiate a high voltage spark for ignition for 7 seconds. If the flame is not sensed within the 7 seconds the control board will repeat the sequence twice more. If all 3 attempts at ignition fail, the unit will enter a lockdown mode.

Common failures:

1. Blower operates but insufficient air flow due to blockage in the air chamber from wasp nests or other intrusions. Clean out air chamber.

2. Sail stuck causing sail switch to not actuate. Free up sail (WD40 maybe).

3. Bad sail switch. Replace switch.

To make troubleshooting easier, download the service manual for your model. There may be a troubleshooting flowchart that you can follow.

Jim something that I learned this summer when my heat went out that may be worth adding to your document (which looks great BTW). The thermostat on my unit sends the signal first to the roof mount AC then on to the furnace. I had a faulty connection at the AC that prevented my furnace (and AC) from running.

[Jagiven]

Originally Posted by M109pilot

I don't even think the blower comes on. I wild hear that, I think.

Most RV furnaces are noisy, Not sure in your Eagle, I would think you would hear it.

If it is not cycling on at all, I would start at your thermostat. Is it electric? Does it have its own internal battery? When was it last replaced?

Test if it is the thermostat, is to pull it off the wall, and jumper across the correct terminals to complete the circuit. If your thermostat controls both the heat and AC, you just have to figure out which two wires to jumper.

It could be a loose wire that the thermostat or even at the furnace connection.

Some control boards will flash an error code, unfortunately most furnaces are installed in away that it is almost impossible to get to without pulling the furnace .

[Bookemdanno]

Not for nothing, but I believe some folks have had to replace the “secret” reset switch and it fixed their problem.

[Rustic Eagle]

Originally Posted by TaftCoach

snip......The thermostat on my unit sends the signal first to the roof mount AC then on to the furnace......snip

Same as mine..., and standing under the ceiling A/C plastic cover you can hear the relay 'click'.

Bob

[theracqueteer]

Originally Posted by M109pilot

But the stove works?

You may have low gas pressure due to faulty regulator. The stove will still light but not enough pressure for the furnace to light. My water heater would not light for that reason.

[M109pilot]

I'll have to research the wiring.
When I have the gear switch to the heat position, I can hear s sound outside at the furnace. Not a clicking sound but a tone. When I turn the heat off, that tone stops.

[M109pilot]

I haven't used the gas for heating water.
How can I test that regulator?

[JimD]

Originally Posted by M109pilot

I'll have to research the wiring.
When I have the gear switch to the heat position, I can hear s sound outside at the furnace. Not a clicking sound but a tone. When I turn the heat off, that tone stops.

If you are hearing a sound out at the furnace that means the furnace has been told to "turn on ". The blower should easily be heard at this point. You may be just hearing a motor hum meaning the blower motor is being fed power but is not turning.

The first thing I would check is to see it the blower is free to rotate. You will know when the blower is running as they are not quiet.

[theracqueteer]

Originally Posted by M109pilot

I haven't used the gas for heating water.
How can I test that regulator?

You need a special LP gas meter. I had a mobile tech check mine as he was there for some other work at the time. It may be easier and cheaper to buy and install a new regulator. If it fixes the problem your good to go, if not then you have a spare. Regulator failures are fairly common.

[pconroy]

Originally Posted by M109pilot

Thanks, guys.

I don't feel comfortable using electric heaters at night while I'm sleeping. Maybe I'm being paranoid?
I also like to have the furnace running at night just to keep some heat moving through the floor. I don't want to risk my pipes freezing. I leave the furnace on about 55 at night. Again, maybe I'm being paranoid.

You're getting great help - but as someone who winter camps frequently, I can chime in a little bit.

First - see if you can work through your issues with electric heaters. We bought one from Target, we run it on the Low (700 watt) setting, and it's amazing how well it works in our motorhome!

Running it on the lower setting ensures the cord won't overheat - if that's one of your concerns.

And if you wanted, you could run two heaters, both on the low setting and really get your camper toasty.


Second - no, you're not being paranoid about your pipes freezing, but know that we've survived dips into the mid 20's *F temps without having anything freeze.

And finally - when our furnace was having trouble, it ended up being the sail switch.
Good luck!!

[M109pilot]

HEAT UPDATE!
Called dometic yesterday. They sent me a service manual for my furnace.
A buddy came over tonight with his fluke. We started troubleshooting and found that we have sufficient power to the board in the furnace. What a Pita it was to get the furnace out. Makes me wish I had an access panel on the side of the camper. Didn't find any debris in the unit itself. We were able to spin the fan too. This is weird but after dying all this, we turned the heat on and it works like it should. It's it possible that maybe the sail switch was stuck?

Jason