So the heater in my 1995 Bigfoot TC is having some issues. When I plug the camper into 110V it works fine. When I switch it over to the battery the ignitor does not click but the fan does turn on. I replaced the battery thinking it was not getting enough juice but that has not solved the issue. Wondering where to look next? Any advice is appreciated. Thanks for your time.

It sounds like the fan is not running fast enough on battery power. When you are plugged in to 110V the converter will be running your DC voltage at around 13.5 - 14V. The battery will only be about 12.6V on full charge. The fan needs to run fast enough to make the sail switch turn on for the ignitor to fire. Either you have a poor connection that is dropping some voltage on the way to the furnace or there is some blockage in the furnace output side or the return air (feed) side. Given the age of your camper a poor connerction is the first place I would look. While the fan is running on battery power, measure the voltage at the battery and at the furnace. The furnace connections will probably be hard to get to, but that is the only way to really know if you have a voltage drop. The voltage at the furnace should be no more than 0.1 to 0.2V below the battery voltage. Any more than that and you will need to check / retighten all the connections at the battery, the DC fuse block, and the furnace.You should also look for any air blockages in the ducting if you have that type of furnace.

My first guess - your battery is not grounded well. That would one of the few reasons your 12v converter can light it but a brand new battery won't. It's grounded enough to spool the fan, but the voltage drop is enough to not allow the igniter to fire.As a quick troubleshooting test - Try running a regular car-type jumper cable from the ground of the battery to the metal casing of the furnace and see what happens. Basically, run a good ground to the furnace.Also see if the fan speeds up when you do this.

I knew I came to the right place. Thank you for the suggestions. I'll try all of them starting with the ground first since it's the easiest. I should have time tonight to take a look. I'll report back on what I find. Thank you again.

I agree that it could be a wiring problem causing low voltage to the heater (specifically to the blower motor).However it could also be a problem with the "sail switch". You can see the sail switch at 2:05 in this YouTube video (note that depending on your make/model the switch may be slightly different or in another location).Cheers,-Mark

I'm out at the camper right now working on this problem. The fan is noticeably faster running on 120 volt shore power. The battery is fully charged and the voltage hardly drops when the fan kicks on. I ran an external ground from the battery to a jack with jumper cables but that didn't help. I also ran it directly to the heat frame and it started to smoke. Next question, and excuse me if this is dumb. Could the battery be hooked up backwards? I bought the unit with this problem and here is what I'm finding. There is a black cable going to the (-) on the battery and a white cable going to (+). Tracing the cables as best I can (they disappear for a moment behind a cabinet and I can't see them) the black cable from the battery runs to the inverter. The white cable disappears and I can't trace the entire thing. All I know is at the jack mounting bracket on the outside of the camper I have a white cable (very similar to the one hooked to positive on battery) and a green cable that comes off the inverter. Could this white cable be the one on the (+) of the battery? If it was hooked up backwards would anything actually work?

Heater Ignitor Works On 110V But Not Battery | Good Sam Community

12 Replies

Boatycall
Explorer
Nov 07, 2014
My first guess - your battery is not grounded well. That would one of the few reasons your 12v converter can light it but a brand new battery won't. It's grounded enough to spool the fan, but the voltage drop is enough to not allow the igniter to fire.

As a quick troubleshooting test - Try running a regular car-type jumper cable from the ground of the battery to the metal casing of the furnace and see what happens. Basically, run a good ground to the furnace.

Also see if the fan speeds up when you do this.
2oldnslow
Explorer
Nov 07, 2014
It sounds like the fan is not running fast enough on battery power. When you are plugged in to 110V the converter will be running your DC voltage at around 13.5 - 14V. The battery will only be about 12.6V on full charge. The fan needs to run fast enough to make the sail switch turn on for the ignitor to fire.

Either you have a poor connection that is dropping some voltage on the way to the furnace or there is some blockage in the furnace output side or the return air (feed) side.

Given the age of your camper a poor connerction is the first place I would look. While the fan is running on battery power, measure the voltage at the battery and at the furnace. The furnace connections will probably be hard to get to, but that is the only way to really know if you have a voltage drop. The voltage at the furnace should be no more than 0.1 to 0.2V below the battery voltage. Any more than that and you will need to check / retighten all the connections at the battery, the DC fuse block, and the furnace.

You should also look for any air blockages in the ducting if you have that type of furnace.

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Heater Ignitor Works On 110V But Not Battery

12 Replies

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