Suburban Furnace Turning on by Itself

dfury77 · 07-11-2018, 03:35 PM

We own a 2018 Salem Cruise Lite 197BH. When we arrived at the campground a few days ago I noticed the furnace fan was running. I checked the thermostat to ensure it was in the "off" position, and within a few moments the furnace shut off.

Four other times in three days the furnace has switched on, and actually ignited/ran etc. In each case I have validated that the thermostat is in the "off" position. I even popped the cover off the thermostat to ensure the contacts were not touching. I cannot see any broken wires or damage. Everything has worked well until recently.

It was a very warm weekend with temps around 75 degrees, and we were actually running the wall mounted AC. I have reached out to the dealer, but am curious to know if anyone else has experienced this... You always hear about furnaces not working when you need them.. so having it just decide to turn on randomly is a bit weird..

For now I've disconnected the battery while it is in storage to stop it running and causing problems.

Johnfort · 07-11-2018, 03:53 PM

Quote:

Originally Posted by dfury77

We own a 2018 Salem Cruise Lite 197BH. When we arrived at the campground a few days ago I noticed the furnace fan was running. I checked the thermostat to ensure it was in the "off" position, and within a few moments the furnace shut off.

Four other times in three days the furnace has switched on, and actually ignited/ran etc. In each case I have validated that the thermostat is in the "off" position. I even popped the cover off the thermostat to ensure the contacts were not touching. I cannot see any broken wires or damage. Everything has worked well until recently.

It was a very warm weekend with temps around 75 degrees, and we were actually running the wall mounted AC. I have reached out to the dealer, but am curious to know if anyone else has experienced this... You always hear about furnaces not working when you need them.. so having it just decide to turn on randomly is a bit weird..

For now I've disconnected the battery while it is in storage to stop it running and causing problems.

There are two wires that connect for a heat call in the thermostat. One is 12v and the other is the heater circuit.

Somewhere in your system these wires my be shorted together, or intermittently shorting together.

Where the wires go into the heater find the non-12v thermostat wire and disconnect it. If the problem goes away, you'll have to chase out the wires for contact. Screws run through them, stripped insulation etc. If that does not solve the problem, its probably in the furnace.

dfury77 · 07-12-2018, 11:16 AM

Thanks for this info! Today when I checked the thermostat the furnace started running even with the thermostat completely removed. What was interesting was that when the furnace shut off, and I tried to start it again by connecting the red/white wires (the ones that go into the thermostat) the furnace wouldn't activate. Not sure if that proves anything, or helps... Still waiting to hear back from the dealer.

Johnfort · 07-12-2018, 11:18 AM

Check for 12v on BOTH wires. If so, the are probably stapled or screwed together.

Scrapper · 07-12-2018, 12:38 PM

Another thing that can happen if the side of the trailer where the furnace is in direct sun on hot days it can get hot enough around the control board to turn the fan on. Having a RV with tan or darker colors will absorb the heat more. I had it happen on my old Wilderness that was sitting in the sun all day and had dark trim where the intake and exhaust was.

Johnfort · 07-12-2018, 01:23 PM

Quote:

Originally Posted by Scrapper

Another thing that can happen if the side of the trailer where the furnace is in direct sun on hot days it can get hot enough around the control board to turn the fan on. Having a RV with tan or darker colors will absorb the heat more. I had it happen on my old Wilderness that was sitting in the sun all day and had dark trim where the intake and exhaust was.

VERY good point. Does the gas come on when it self starts? If not, this is a high probability along with a wire short. If the burner does come on, it's not the culprit.

dfury77 · 07-12-2018, 01:59 PM

Very good suggestion! Sadly my trailer is white in that area, and yes the furnace does ignite when it runs on its own. I will test the wires coming from the thermostat to see if 12 volts is showing on both... My other thought is that maybe the control board is bad and starting the startup process on its own....

wmmhvac · 07-12-2018, 02:32 PM

If you disconnect the wires that connect to r and w on the termostat the unit should not run. If it does go to the furnace and disconnect the same two wires where they hookup, if it runs, you could have control board problems. I'am thinking it will not run, when disconnected at furnace. so probably shorted wires r and w usually they use red and white. When wires are disconnected at both the thermostat and the furnace. make sure they are not touching each other and check with continuity meter they should have no continuity if they do they are shorted somewhere probably a screw or nail. if there is a extra unused wire in the thermostat wiring you could substitute for the r or w

Johnfort · 07-12-2018, 02:39 PM

Quote:

Originally Posted by wmmhvac

If you disconnect the wires that connect to r and w on the termostat the unit should not run. If it does go to the furnace and disconnect the same two wires where they hookup, if it runs, you could have control board problems. I'am thinking it will not run, when disconnected at furnace. so probably shorted wires r and w usually they use red and white. When wires a disconnected at both the thermostat and the furnace. make sure they are not touching each other and check with continuity meter they should have no continuity if they do they are shorted somewhere probably a screw or nail. if there is a extra unused wire in the thermostat wiring you could substitute for the r or w

I totally agree with Mr HVAC. Pro- advice.

If the board is bad, be SURE to use a Dinosaur brand circuit board. Similar cost, american made and trouble free. Same thing applies to your water heater and fridge.

Available on Amazon, or look up on internet and order it direct. Same cost or less, same fast service, saves the small company middleman profit.

Scrapper · 07-12-2018, 02:40 PM

Here is the service manual for almost every Suburban furnace if that is what you have.

dfury77 · 07-12-2018, 03:54 PM

Unhooked the red and white wire from the thermostat...checked for continuity and sadly the multimeter started screeching..so looks like a shirt is a likely culprit.

I hate to think what it will take for the dealer to fix this once they get back to me..ugh

wmmhvac · 07-12-2018, 04:05 PM

For that test to work properly the r and w wires need also to be disconnected at furnace, if they are still connected at furnace you will get feed back on meter

larry2c · 07-18-2018, 06:34 PM

I've not had your issue but I have had some strange issues with our thermostat and re-initializing the thermostat cured the problem(s). There is an instruction in the manual for re-initializing the thermostat.

Johnfort · 07-18-2018, 06:37 PM

Quote:

Originally Posted by larry2c

I've not had your issue but I have had some strange issues with our thermostat and re-initializing the thermostat cured the problem(s). There is an instruction in the manual for re-initializing the thermostat.

OP mentioned that the furnace came on with the stat completely removed. Has to be a shorted stat wire or a bad board.

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