Furnace won't turn on

[Henel]

We have a 2015 jayco 1209sc pop up.
Propane is hooked up, stove works
Battery fully charged
Fuses are fine
We are plugged in to power
Thermostat is on, other switch for temp control is all the way up
Overhead lights work no issues
Furnace won't turn on?
Switch on furnace only says "reset" or "off"
How do we turn furnace on? Nothing is happening.
We've only used the heat one other time last October with no issues, but we can't remember how we did it. Manual has only one page of instructions and it's very vague.

[RogerR]

There is a lot on the search button above about furnace problems.


What is you exact model furnace, that always helps get precise advice.


Did you hit the reset button?

Is you fuse supplying 12 volts to the furnace good?
Do you have voltage to the thermostat?
Have you jumped the thermostat wires to see if it works with no thermostat?
Does the fan run even though it doesn't light?

If the fan runs but no heat did you check the sail switch that prevents ignition if there is no air movement.
If the fan runs, the sail switch is moved you may have an igniter problem that I have never had so I can't help there.



There is a lot more but try a few of those, hope this helps.

[JimD]

The way these furnaces work is that the thermostat simply puts 12 volts on a single wire that goes to the furnace. This tells the furnace that heat is required. When the thermostat reaches the set temp, the 12 volts is removed.

The furnace is in control of everything it does. When it sees the 12 volt signal to turn on, the blower should start after which the burner will start if a sensor detects correct air flow. The burner won't start if there is insufficient air flow. This is a safety feature so the furnace doesn't go up in flames.

Anyway, with your problem it sounds like nothing is happening. This most likely is being caused by the lack of either the 12 volt power feed to the furnace (plus ground) or a missing 12 volt signal from the thermostat.

A voltmeter would be very helpful in this case. You would have to poke around inside the furnace to see what is missing and then go from there.

Sure it could be a bad control board in the furnace but I would first lean toward the inputs that need to be there.

To sum up this long-winded response, you need to have:

12 volts
Ground
12 volts on a signal wire from the thermostat

[Henel]

Furnace Model # 7916-11, all fuses are good, propane tank works as stovetop is fine. Where would we check voltage to thermostat? All wires look like they are connected

[RogerR]

A simple multimeter like this one on Amazon is handy and cheap, also Harbor Freight and anywhere for about $10.


Set it to DC 10 to 20 volts or whatever setting covers that area. Test with it on by touching the red one to the plus side of the battery and the black one to the minus or negative side. It should read between 12 and 13 volts or so. If it is below 12 volts your battery is low.



Then go to the wires and put your tester black on metal frame material and touch it to each or the screws holding the wire to the thermostat. Should also show about 12 volts. If you don't get anything then you are not getting any power to the thermostat. Go to the appropriate fuse and check it.

Hope this helps.

[JimD]

Here is a sample of the wiring for a typical heat/cool thermostat. I don't know if you have AC or not. I have also attached the Coleman thermostat catalog that shows the wiring for all of their thermostats. Might give you a starting point for measurements.

[Seann45]

Open your furnace compartment and look at the furnace somewhere on it (usually the top there is a rocker switch if this has been shut off then the furnace wont work.. I found this out the expen$ive way