Is the furnace blower powered from chassis batteries?

Kvw613 · 01-16-2019, 06:53 AM

While boondocking a few days ago, I ran the furnace for a few hours. Later I tried to start the engine and only got the solenoid click. Running the generator for a few minutes and depressing the aux battery start switch helped get us going. I am wondering if the furnace blower is powered by the chassis batteries, and dragged them down.

2002 Itasca Horizon 36LD

Teamfoxy · 01-16-2019, 07:38 AM

The furnace blower is powered by the coach batteries. Cold weather does bring out the problems in batteries and I would also check the terminals for corrosion.

powercat_ras · 01-16-2019, 04:20 PM

Furnace will draw about 8 amps when the furnace blower is running so at 33 % duty cycle it will use about 2.7 Amp-hours per hour, or 63 amp-hours per 24 hours. Other things are drawing a little battery all night, too like the propane detector. Battery resting voltage will drop to 11.9 with 40 % left and 11.6 with 20 % left. So if one has the two older original NAPA batteries that together only have 60-80 amp-hours of capacity left (100 when brand new), it would not be unusual to go from 80 % to 20 % in one night using the propane furnace.

BobC · 01-16-2019, 06:37 PM

The only two things that I can think of that would cause your furnace blower to run down your chassis battery are:

1. An interconnection between the house and chassis batteries installed by a previous owner. This might have been done in order for the chassis battery to charge from the converter/charger.*

2. A faulty Aux Battery solenoid that's stuck in the "on" position.

You can check out the above by disconnecting the positive cables from both house and chassis batteries and check for continuity between the disconnected cables with a multimeter. If there is more than one wire connected to either of the two positive battery posts, you'll need to check all of them. This will tell you if the two batteries are interconnected. If they are, you'll need to to disconnect the Aux solenoid to see if it's the cause. If it's not, then you'll need to get creative in finding the source (and fix) of the interconnection.

If there's no continuity, then something else is draining your chassis battery. If your chassis battery is on it's last legs it may not be able to support normal "parasitic" loads: https://winnebagoind.com/resources/s...%20Systems.pdf

*The correct way to do this would be to install a Trik-L-Start, Amp-L-Start or other such device.

jeepster05 · 01-16-2019, 07:50 PM

I have the same issue of the furnace blower draining my batteries when it's extremely cold outside and the blower runs frequently. I have a 2019 27pe and had a 2006 Outlook that done the same thing. I disconnected the ground wire on my battery and put an amp meter between the post and battery cable. It shows a little over 5 amps when the blower is running. other than the blower not sure what else could be the cause. Batteries do not drain overnight on warmer nights. I'm talking dry camping..

powercat_ras · 01-19-2019, 12:08 PM

> furnace blower draining batteries ...

This might be why. The colder it is the more we use the furnace and if the batteries are outside the heated area of the camper the colder they are, too.

Diesel-Lover · 01-20-2019, 10:12 AM

I vote for a wiring miss or as mentioned above solenoid linking the house and engine battery together. Battery buddy on engine battery will isolate it automatically at about 50 percent capacity, else just use a mechanical cut off switch that way your engine battery is isolated fully.

BobC · 01-20-2019, 10:44 AM

If I'm reading correctly, both jeepster05 and powercat_ras are commenting on issues that could drain the house batteries. The OP's question had to do with his chassis batteries, which should not be affected by the furnace unless there's something amiss.

chrisnlbc · 01-23-2019, 05:33 PM

Quote:

Originally Posted by powercat_ras

Furnace will draw about 8 amps when the furnace blower is running so at 33 % duty cycle it will use about 2.7 Amp-hours per hour, or 63 amp-hours per 24 hours. Other things are drawing a little battery all night, too like the propane detector. Battery resting voltage will drop to 11.9 with 40 % left and 11.6 with 20 % left. So if one has the two older original NAPA batteries that together only have 60-80 amp-hours of capacity left (100 when brand new), it would not be unusual to go from 80 % to 20 % in one night using the propane furnace.

Very good to know about the Napa batteries being stock. I just replaced mine on my 2018 22r. They had gone down on cold nights. I figured they were the stock because they still had the VIN Tags on from Winnebago. I bought my coach used with 10k miles. So a trip to Costco and replaced with two of their RV Interstates. Not my first choice, but price and convenience was right.

I also had to touch up my battery area, one of my old batteries blew its vent. I had to clean and repaint. But all good now. Testing this weekend on a desert trip.

cshluver · 01-23-2019, 08:10 PM

I agree with Bobc the chassis battery should not be drawn down while using the furnace.
if the battery on your 2002 is original, give thanks that's its lasted this long.Most likely connections or the battery is on it's last legs heightened by the cold conditions.

JoeC · 01-23-2019, 08:20 PM

Ditto, Bob C. You have a faulty battery cross connect or your starter battery is aging and can't handle its parasitic loads and cold weather at the same time causing a coincidental loss of power.

CharlesMoore · 01-24-2019, 10:45 AM

A lead acid battery only has so many charge - discharge cycles. The deeper you discharge the battery the number of charge- discharge cycles the battery will provide reduces. This can be a surprisingly short number of cycles. The following link will take you to a site that gives a lot of information that will save you $$$ by spending 10 minutes:

https://batteryuniversity.com/learn/...ased_batteries.

Take this from a ocean sailor that has spent multiple thousands for batteries over the last 15 years.