Furnace starts out great & then later not?

A battery that reads only 12 volts is technically dead. 12.6-12.7 is fully charged. Older batteries reading low will not have the oomph to continually maintain the needed blower RPM to keep the sail switch closed allowing the furnace to blow cold air and freeze you out. A battery reading 10-11 volts will run the blower motor and it will sound as if it is running ok, But you need that RPM that only a fully charged battery can provide.

If related to battery operation then most likely a low voltage sail switch issue.

If not, could be an oil trap in the copper line to the furnace IF it works when warm (lower viscosity) BUT not when cold (higher viscosity). This type of issue is probably more common with using propane bottles then with frame mounted propane tanks..

Ok, yes I got our propane in Los Angeles.
1st night in New Mexico, it was about 8 degrees & we had no electrical hook up & ran the Geni for a while then the furnace ran strictly on battery.

& did not stay hot all night, very cold night for us.

Next night we had electrical hook ups & same thing, temps were about 10 degrees.

Then back to Arizona & it was about 16 degrees it seemed to keep warm through the night.

Then last night here in Laughlin we just just ran the electric heaters, so don't know if it would kept warm, our last night will be boon docking in the desert so we'll see how it works that night.

Blanco, have you bought more propane since this problem started?

What is sold as "propane" differs quite a bit based on when & where you buy it. If you filled up near LA in warmer weather you well could have gotten nearly straight, if not straight, butane.

Butane boils at 30 to 34 deg. F. so if it's that cold or colder you will have little to no gas vapour. In other words you could run out of gas with a full tank of butane.

By comparison propane boils at anything above about -44 deg. F. so you'd still have lots of gas vapour down to well below most people would be camping in.

I am having the same problem on a new MH.
I get the E02 under voltage shutdown fault code. The inverter shows 11.0 on the input voltage meter

We are in Colorado Springs with some extreme cold so having to wonder if it is related to that?

Still I am not understanding why as we are connected to a 50 amp RV park plug. I have to start the MH engine to get the furnace to kick back on. Then all works fine for an hour or two after I turn off the MH engine and then the furnace shuts down again.

Everything is brand new

Ok, camping right now & I've learned, that it's not a battery issue being the battery seems to stay above 12 volts or more & still stops blowing hot air after a while?


Yet turning it off & turning it back on seems to get the heat going again ?

So what you guys think?

Camp, Forrest, Camp! wrote:
I had a similar problem in my 1985 Lance. In my case, the furnace would come on and run one complete cycle with no problem. When it came on the next time the thermostat called for it, it wouldn't light and would blow cold air until morning. If I flipped the on/off switch to off, then back on, it would again work for one cycle, then go cold. In the end, my problem was the control board. The new one not only corrected the problem, but prevented the cold air thing.

Here's the explanation of what was going on:
- The root problem was a problem with the control board that it was preventing it from lighting the second time. Resetting it with the on/off switch reset the board.
- The old board did not have a "lockout" mode, so when it did not get confirmation of a light, it would blow air constantly as a safety precaution. This would ensure that the furnace did not overheat and start a fire. Since that furnace draws outside air, we woke up freezing with a broken toilet.
- The new board had the ability to shut everything down, so if it fails to light, it tries two more times, then calls it quits. Ten minutes later, it tries the trio again. After three total routines, it locks the system down until the on/off switch is reset. You may not have heat, but at least you don't have single-digit air getting pumped into your camper.

Where is this control board?

Or are u talking about the one on the wall with the remap settings?

I've been hearing from many that it's likely a voltage drop in the battery.

I was gonna go for 3 6 volt batteries next, but they won't fit in the Lance battery box.

So now this has me wanting to get a brand new biggest deep cell 12 volt I can for the camper hoping that fixes it.

But this control board sounds about right & being yours is also a1985 just like mine, could be a common issue?

Please tell me the the control board is super easy?

I had a similar problem in my 1985 Lance. In my case, the furnace would come on and run one complete cycle with no problem. When it came on the next time the thermostat called for it, it wouldn't light and would blow cold air until morning. If I flipped the on/off switch to off, then back on, it would again work for one cycle, then go cold. In the end, my problem was the control board. The new one not only corrected the problem, but prevented the cold air thing.

Here's the explanation of what was going on:
- The root problem was a problem with the control board that it was preventing it from lighting the second time. Resetting it with the on/off switch reset the board.
- The old board did not have a "lockout" mode, so when it did not get confirmation of a light, it would blow air constantly as a safety precaution. This would ensure that the furnace did not overheat and start a fire. Since that furnace draws outside air, we woke up freezing with a broken toilet.
- The new board had the ability to shut everything down, so if it fails to light, it tries two more times, then calls it quits. Ten minutes later, it tries the trio again. After three total routines, it locks the system down until the on/off switch is reset. You may not have heat, but at least you don't have single-digit air getting pumped into your camper.

Blanco1 wrote:
Where would I find the converter & how would I check it?

Converter is generally in close proximity to the main fuse and breaker panel.
If you have about 13.6 volts at the fuses the converter is fine.

Now you need to remove the furnace for inspection. If you are not comfortable with that you will need to go in for service.

There is no external knob or switch that is going to resolve the furnace trouble.

I had a similar problem and it turned out to be a bent sail switch. The furnace would fire up initially, but on the second or third cycle the fan would come on for a few seconds and then shut off. Turning the furnace off and back on would revive it for a cycle or two.

It took the dealer some time to figure out the defective switch.