Born Free Leap'n Lions RV Club Info & Discussion Forum

Enjoying the cool weather in the Rockies but suddenly we have a problem. I turn on the furnace, as usual, and the purge fans start running but the burner doesn't light. Repeated the operation several times without success.
Remembered that the last time I used the furnace the generator was running so I tried that and it ran properly. Turned the generator off and "no soap" back to no burner.
The batteries were showing 2/3rd charge but I don't know what that equates to in actual line voltage. Shouldn't the furnace be able to function properly from battery power alone? I seem to remember running the furnace on just the batteries in the past, but nowdays my memory isn't to be trusted with important details. Anyone have a suggestion?

Hey Woodie, the furnace needs either the battery or shore electric and propane. Electric to run the fan and propane for fuel. Yes, it will run off the batteries with the propane.
I am sure someone will help. In the meantime, click on search at the top of the page, then click on Gen discussions, and write in furnace problems, and it will bring up info on furnace problems. You may find your answer there.
Good luck, see ya down the road, jerseypete

This might not be your problem but it happened to us. Furnace fan ran but it would not light. Mobile RV tech pulled out the furnace from inside the coach. There were two tiny gnats that were inside the burner tube. This prevented propane from flowing and igniting. Ever since then I have placed blue painters tape over the exterior furnace inlet/outlet. Just remember to remove the tape before you turn the furnace on!

John, that is what I also do with blue painter's tape.

Bill

jeleuen wrote:This might not be your problem but it happened to us. Furnace fan ran but it would not light. Mobile RV tech pulled out the furnace from inside the coach. There were two tiny gnats that were inside the burner tube. This prevented propane from flowing and igniting. Ever since then I have placed blue painters tape over the exterior furnace inlet/outlet. Just remember to remove the tape before you turn the furnace on!

I agree that the orifice must be open and clear for the burner to light properly but my problem is that it will light and run when hooked to shore power or if the generator is running but will not light when attempting to do it on the coach batteries alone.

IMO, every handy man should have a DVOM (digital volt ohm meter) and learn how to use it to the point of being able to use it safely to perform basic continuity and voltage measurements. Today you can get a digital voltmeter, with great precision, for as little as $3 from Harbor Freight.

Woodie,
One probable explanation for this furnace problem is low battery voltage. A low voltage could cause the fan to run slow and the sail switch to not actuate. There can be several conditions that could cause low voltage at your furnace and still show an adequate charge at the monitor panel.
1. Too many devices on at the same time. Each light, appliance or device reduces the 12vdc supply a little. Turn on enough appliances and eventually the voltage will become unacceptable.
2. A marginal fan motor. Dirty bearings or bad windings can slow the motor under marginal power but it would seem to work OK when it has the full 13+VDC from the converter. Cleaning/lubing the motor and sail switch mechanism could fix this problem.
3. Bad 12VDC connections to the furnace could result in reduce voltage to the furnace.

If you could give us the benefit of some simple voltage measurements, we could offer you a more precise diagnosis. The voltmeter would enable that. It would also allow you to test light bulbs, fuses, campground power, batteries, battery charging, wiring problems, and on and on.

I believe that anyone who understands how a flashllight works can learn how to use a DVOM for the basic measurements in a very short time with the proper instructions. Proper instruction is key It is very easy destroy stuff and injure people without proper training.

Mike

Mike, I appreciate your thoughts on the subject. We returned home this afternoon and I have access to my shop. I will try to duplicate the problem and take some voltage readings. Hopefully the cause is simply low voltage and some steps can be taken to reduce the load on the batteries when use of the furnace is anticipated.
I was on the road when the problem popped up and with the storage space limitations on a BF I travel with a simple tool that detects the presence of voltage and continuity but doesn't display the actual voltage present. I'll do some testing and post the results. Mike H

As a followup on the furnace problem I was experiencing, I went out to the coach this morning after driving it around 500 miles yesterday. Nothing had been operating that should have discharged the house batteries and when I turned on the furnace it fired up properly. That would lead me to believe that my problem was low battery voltage while in the mountains. When the problem appeared the coach had been sitting for three days with minimal DC usage but still the batteries would not have been in optimal condition.
Hopefully the furnace will continues to operate with good battery charge as we quite often find ourselves without AC service where we are camped.

41Woodie wrote:As a followup on the furnace problem I was experiencing, I went out to the coach this morning after driving is around 500 miles yesterday. Nothing had been operating that should have discharged the house batteries and when I turned on the furnace it fired up properly. That would lead me to believe that my problem was low battery voltage while in the mountains. When the problem appeared the coach had been sitting for three days with minimal DC usage but still the batteries would not have been in optimal condition.
Hopefully the furnace will continues to operate with good battery charge as we quite often find ourselves without AC service where we are camped.

Woodie,

I don't know what minimum voltage you should expect the furnace to keep running. That begs the question, will the furnace operate at a reasonable voltage? And, what's reasonable? I'm pretty sure mine continues to operate at 10.5 VDC . That's at the point that you are stressing the batteries quite hard. But there have been times when I've said, "To heck with the batteries. I'm cold and don't want the pipes to freeze!"

Any other opinions?

Mike