boondocking heater issues

[w0hva]

A year ago I purchased a new Bullet Crossfire. I spend about 10 days every fall at a campground where no power is available. I use a generator and solar panels to charge the battery. The generator is run about 3 hours daily and the solar panels are connected during daylight hours. No one is in the camper most of the day and the only thing turned on is the refrigerator running on LP gas. The heater will start, ignite and then go out. Last fall this cycle has repeated all night. I measured the voltage at the battery and it was showing 12.3 V when I noticed the issue. This summer I had the camper at my dealer and was told there was not a problem since the heater requires 12 volts to operate. My old camper would operate the heater down to 11 volts. I have installed a second battery to possibly increase the time before the voltage drops below the critical value. Am I right in assuming the heater should work at a lower voltage/

[Canonman]

12.3 vdc is about 70% charge. 12.0 is right at the 50% you don't want to go below if possible. I'm betting there is another problem with the furnace. The furnace appears to be short cycling.
Here is some information that may help you: https://www.everything-about-rving.c...5-minutes.html

[Canonman]

Just checked out this video. Pretty comprehensive.

https://www.youtube.com/watch?v=Gm_xbVpDOGs

[w0hva]

The furnace works fine when the camper is connected to shore power, in fact starting my generator while the furnace is acting up resolves the problem. That's why I was wondering about the voltage minimum.

[flybouy]

Originally Posted by w0hva

The furnace works fine when the camper is connected to shore power, in fact starting my generator while the furnace is acting up resolves the problem. That's why I was wondering about the voltage minimum.

I suspect the sail switch is the culprit of your issues. It doesn't take a lot of voltage (about 12 vdc) or amperage to operate the control board, open the gas valve, and ignite the gas. What does take a lot of power is the blower motor.

The furnace blower motor not only blows the air from the heat exchanger into the camper but it is also the exhaust fan for the burner. The blower motor is what operates the safety device called a sail switch. If the fan doesn't blow enough air to operate the sail switch the furnace sees that as a CO danger and will not allow the furnace to operate. Saying the furnace works when on shore power indicates that the furnace needs the extra voltage that the converter is supplying to operate the sail switch.

The sail switch could be obstructed (dirt, lint, pet hair) opr it could be bent creating friction. The only way to diagnose and repair is to remove the furnace if there's no outside access.

[chuckster57]

Originally Posted by w0hva

The furnace works fine when the camper is connected to shore power, in fact starting my generator while the furnace is acting up resolves the problem. That's why I was wondering about the voltage minimum.

As Marshall said, it’s the sail switch. The motor isn’t spinning fast enough, I would load test the battery(s) before digging into the sail switch.

[ChuckS]

I’d also take a few minutes and check the wire terminal connections on the furnace control board.. if the motor power wire spade connection is loose, etc it will give you issues when the blower motor tries to spin up..

And of course check the ground cable from the battery to frame ..remove the frame end and make sure there is bare metal that the cable is hooked to or you will have issues trying to draw a larger amp load

[w0hva]

Thanks all for your input. According to Dometic the heater requires 10.5 to 13.5 volts to operate properly. The sail switch and main board have been replaced and the batteries are new. I am thinking at this time there is a design issue in the heater cabinet that is causing poor air flow. I will do my best on my upcoming trip to conserve battery power and insure the batteries are fully charged before retiring for the night.