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Thread: Furnace Problem

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    Furnace Problem

    I am a Grand Design owner. My furnace doesn't want to work off the batteries. I bought two new batteries. Still no go with the furnace. It turns on but doesn't seem to have the juice to keep going. It works when plugged in and it works when used on my generator. What is my problem?

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    Site Team Second Chance's Avatar
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    The furnace is a 12 volt (only) appliance. It always runs off 12 volts - whether it's the battery alone or the battery being charged by your generator or shore power. How old is your battery (or batteries if you have more than one)? Sounds like you may have one or more bad cells in a battery. It doesn't sound like it's a furnace problem.

    Rob

    PS - some information about your RV model and year in a signature would help others answer your questions.
    U.S. Army Retired
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    2020 Solitude 310GK-R, MORryde IS, disc brakes,
    Sailun LRG tires, solar, DP windows, W/D
    (Previously in a Reflection 337RLS)
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    King Pin
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    Rob is spot on with his comment. You appear to have a battery issue.

    Like he says, it takes 12V to run the furnace. When you plug in, the converter supplies 12V instead of the battery. This is why it runs when you're plugged in. But when not plugged in, you need to have good batteries to run the furnace which takes quite a bit of power. I'd pull your battery(ies) and take them to a battery shop and have them tested. If you have a volt meter, you can unplug from shore power and see if your batteries are reading 13.5-13.6VDC. Anything less, and there is likely a problem.

    Jim

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    Long Hauler Paul & Deb's Avatar
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    Quote Originally Posted by TucsonJim View Post
    If you have a volt meter, you can unplug from shore power and see if your batteries are reading 13.5-13.6VDC. Anything less, and there is likely a problem.

    Jim
    This brings up a good point or question. In order to properly test the battery, after unplugging from shore power, are you supposed to wait for some period of time before testing? Also, is it better to disconnect the battery from the trailer to get a truer reading? I always get confused by this. Does it make enough difference to matter?
    Paul "Poppy" and Deb Cervone
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    2021 Imagine XLS 17MKE - SOLD ; 2015 Grand Design Reflection 337RLS - SOLD
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    King Pin
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    Quote Originally Posted by Poppy's 5th Wheel View Post
    This brings up a good point or question. In order to properly test the battery, after unplugging from shore power, are you supposed to wait for some period of time before testing? Also, is it better to disconnect the battery from the trailer to get a truer reading? I always get confused by this. Does it make enough difference to matter?
    Yes, I'd wait about 10 minutes or so. Then I'd shut off the disconnect switch before testing.

    Jim

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    Site Team Second Chance's Avatar
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    Quote Originally Posted by Poppy's 5th Wheel View Post
    This brings up a good point or question. In order to properly test the battery, after unplugging from shore power, are you supposed to wait for some period of time before testing? Also, is it better to disconnect the battery from the trailer to get a truer reading? I always get confused by this. Does it make enough difference to matter?
    At least the battery disconnect switch needs to be off so the inverter isn't supplying power to the battery. That would skew the readings since the inverter/charger would be supplying the voltage. Waiting a while to test after disconnecting will give you a better idea of whether or not the battery will hold a charge. The best test, however, is still a load test at a local parts store.

    Rob
    U.S. Army Retired
    2012 F350 DRW CC LB Lariat PS 6.7
    2020 Solitude 310GK-R, MORryde IS, disc brakes,
    Sailun LRG tires, solar, DP windows, W/D
    (Previously in a Reflection 337RLS)
    Full time since 08/2015

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    Quote Originally Posted by TucsonJim View Post
    Rob is spot on with his comment. You appear to have a battery issue.

    Like he says, it takes 12V to run the furnace. When you plug in, the converter supplies 12V instead of the battery. This is why it runs when you're plugged in. But when not plugged in, you need to have good batteries to run the furnace which takes quite a bit of power. I'd pull your battery(ies) and take them to a battery shop and have them tested. If you have a volt meter, you can unplug from shore power and see if your batteries are reading 13.5-13.6VDC. Anything less, and there is likely a problem.

    Jim
    Jim, I believe you have Battle Born LiFePo batteries that read a higher voltage at full charge. If the OP is using flooded cell batteries 12.7v is considered 100% charge.

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    Rolling Along cfowler55's Avatar
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    The OP stated he bought two new batteries. Start by checking the voltage on the new batteries , then check other 12 volt functions - lighting , water pump , etc.. Check your battery connections and make sure the battery disconnect is in the proper position. Report back.
    Charlie
    Vickie & Charlie
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