2018 Freedom Elite 26HE Furnace+Battery issues

[Mark in ATL]

First time posting, so I apologize if I leave out anything important. I barely know what I’m doing, but I’m willing to learn and try! We just returned from a weekend trip and our furnace failed--cold night! 2018 Thor Freedom Elite 26HE, Atwood furnace. It would run for maybe 10 seconds then turn off, and then give up after a few iterations every few minutes. I couldn’t hear it even trying to ignite—just the fan running. Back home, I opened the furnace cover (nothing looked wet, per other threads) and turned off the “Off/Reset” switch. Tried again, and now it runs longer and sounds like it’s trying to ignite a few times. I could smell gas. I tried the bit in the (horrible) manual about running it with LP off and that doesn’t help. Then, I noticed the indicator for battery charge was only one light. It should be full. We ran the fridge off LP while stopped for 3 hours in lovely Plains, GA, but then drove two more hours home, which should have charged the house battery, right? Of note, when we bought the RV this past year, it also had a low battery. The previous owner had an extended warranty and took it in for that and a couple of other minor repairs before we took possession, so presumably the battery was checked/repaired recently by dealer.

We were on shore power when the furnace wouldn’t light. Propane seemed fine—we used the stove with no issues. LP tank is >50% full. Do you think the battery and furnace are related? Any steps to try before I just punt and take it to the shop? Thanks!!

[16ACE27]

Divide and conquer:

If the furnace lighting issue happened while connected to SP then the battery issues are not related.

I would tackle the battery issues first and use a portable electric heater if needed in the meantime.

House Batteries are charged by the Converter if the USE/STORE switch is in USE and you are connected to SP or are running the generator.
House batteries MAY be charged by the alternator if designed to do so on your coach and the BIM is wired correctly (common Thor issue). The USE/STORE switch does NOT have to be in USE for this to happen.

You need to fully charge the house batteries and have them tested. See what their actual status is for you. Do not rely on what may or may not have happened in the past and you really have no idea how badly the batteries have been abused.

Furnace:
Needs 12 VDC from the DC buss and propane from the propane distribution line.
If other propane appliances work fine then you should have propane to the furnace. Test this by lighting ALL burners on your stove for at least 5 minutes.
When the thermostat calls for heat the furnace fan comes on immediately.
The Sail Switch senses enough air velocity to allow lighting the furnace.
The control board opens the propane solenoid valve and starts sparking the ignitor. If flame is not sensed within a given time period the propane valve closes and sparking stops for a "clear out" delay. Then it tries again. You should definitely be able to hear the ignitor sparking.
After 3 attempts the furnace locks out until reset by either the reset swicth by the control board of by removing the "call for heat" at the thermostat.
After the reset you can try the furnace again and the cycle repeats.

The board is a common failure item even if not wet or corroded.
You may have a bad ignitor or a bad gas solenoid.

If you replace the board I recommend the Dinosaur brand board with 3 year warranty.

[Mark in ATL]

Thank you so much for the detailed and insightful reply. I disconnected the house battery and charged it using my car battery charger. It was up to over 13V when I stopped charging. Reconnected, then panel showed full charge. Drove RV back to our parking lot, then panel showed half charge. So, I think I'll replace the house battery. Incidentally, when I got to the lot, I tried the furnace, and it worked! So, I'll just have to wait and see if it fails again.

[16ACE27]

Originally Posted by Mark in ATL

Thank you so much for the detailed and insightful reply. I disconnected the house battery and charged it using my car battery charger. It was up to over 13V when I stopped charging. Reconnected, then panel showed full charge. Drove RV back to our parking lot, then panel showed half charge. So, I think I'll replace the house battery. Incidentally, when I got to the lot, I tried the furnace, and it worked! So, I'll just have to wait and see if it fails again.

How long did you charge? A low/dead battery can take 5+ hours to fully charge depending on the charger. The voltage on the battery just after removing the charger is not representative of it's "actual voltage" as the charger was putting 13+ VDC on the battery and it takes a half hour or so for this "surface voltage" to drop to the battery's actual voltage.

[Mark in ATL]

(I really do barely know what I'm doing!) Charged maybe half an hour. Guess I'll plan on a full charge before replacing. Another naive question: could I take it to AutoZone and get them to test it, or is that only appropriate for auto batteries that need to crank an engine?

[16ACE27]

Originally Posted by Mark in ATL

(I really do barely know what I'm doing!) Charged maybe half an hour. Guess I'll plan on a full charge before replacing. Another naive question: could I take it to AutoZone and get them to test it, or is that only appropriate for auto batteries that need to crank an engine?

Yes, after you fully charge it you can take it to AZ for testing.