Forum Discussion

SlowBro's avatar
SlowBro
Explorer III
Mar 24, 2022

[SOLVED] Bad converter? Low voltage

The voltage in our class A's converter drops as low as 8.2V (measured with a cigarette lighter voltmeter) with a DC laptop adapter attached. Causes the charger to stop and the laptop not to charge. It currently has no house battery connected, though there is a starter battery. After some time the laptop charger stops trying and the voltage stabilizes at 10.9V. Is this a sign of a bad converter, or is this because no house battery is attached?
  • Bobbo's avatar
    Bobbo
    Explorer II
    Mar 24, 2022
    Which converter do you have. Most of the newer converters don't have to have a battery attached, but some of the older ones do require a battery.

    However, the converter voltage should be above 13.2v under all conditions, so it very well could be a bad converter.
  • time2roll's avatar
    time2roll
    Nomad
    Mar 24, 2022
    Verify the low voltage right at the converter output. Once confirmed then replace. Yes virtually all newer converters are made to operate fine without a battery.
  • fyrflie's avatar
    fyrflie
    Explorer III
    Mar 24, 2022
    Verify voltage at the converter as time2roll suggested.
    If good then check voltage at the cigarette lighter. That could be your problem. Or try connecting to a different power source to see what you get.
    Check cheap simple things first.
  • Matt_Colie's avatar
    Matt_Colie
    Explorer II
    Mar 24, 2022
    Slow,

    If you have shore power, why don't you run the laptop on that?

    Also, if you can post the make and model of the converter, someone will know if the missing battery is likely to be the problem.

    Given that it is a 10yo Coachman, it probably was a good one when new.

    Matt
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Mar 24, 2022
    Where are you measuring? Best spot is the converter itself.

    That indicates a high resistance along the line somewhere.. Might just be a bad fuse. Might be $$$$$
  • BFL13's avatar
    BFL13
    Explorer II
    Mar 25, 2022
    Not clear if the 12v socket is in the dash (powered by engine batt) or somewhere in the house (powered by converter/house batt)

    The converter does not supply the dash 12v socket.
  • SlowBro's avatar
    SlowBro
    Explorer III
    Mar 26, 2022
    Just got back from the RV. It's a WFCO WF-9855 converter and shpows 13.1V at the panel so yeah, it's a fuse or wire or something. Got two sockets, both showing low voltage, so I'm thinking it's the wire or fuse. I'll start by swapping the fuse.
  • SlowBro's avatar
    SlowBro
    Explorer III
    Mar 26, 2022
    I believe these cigarette lighter outlets are on the engine 12V system which I believe would place them in front of the battery isolator. Noticed that the engine battery is sitting at 11.1V. Does the isolator cause that much of a voltage drop?

    Edit: Oh no. I'll bet the starter battery doesn't get a charge from the converter at all, and I've been draining it. Probably killed it.
  • SlowBro's avatar
    SlowBro
    Explorer III
    Mar 26, 2022
    Since it was at 11.1V surely some damage has occurred. Will have to replace it. Stuck a car battery charger on it and the cigarette lighter outlets in question jumped to 12.6V. I think this mystery is solved.

    Thanks everyone!
  • Matt_Colie's avatar
    Matt_Colie
    Explorer II
    Mar 26, 2022
    SlowBro,

    Thanks for reporting the progress. The 11.1 on the chassis batter may well have harmed it, so replacing it is not stupid.

    When you find the rest of the problem, that would be good to hear too.

    Matt

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