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alienbogey's avatar
alienbogey
Explorer
May 08, 2019

New House Batteries Now No DC Power

I'm running out of troubleshooting ideas......

DC power was working normally except for house batteries (2) not holding a charge (four hours or so to flat). Batteries were 8 years old and tested bad, took it to a shop that installed 2 brand new 12 volt RV batts.

Got truck camper home from shop and first noted that electric jacks wouldn't work. Then saw nothing 12volt was working in the camper. (Camper was plugged into truck via normal pig tail.)
Plugged camper into shore power and the jacks began to work, took camper off truck. (Needed it off to use truck.) Today I had the time to get back to the problem.

Now, with camper off truck and plugged into shore power or not plugged int shore power I have no DC at all. Facts and troubleshooting so far:

• Both batteries show 12.65 volts
• One positive terminal was noticeably warmer than the remaining positive and two negative (126 degrees vs 65)
• Found no loose/unattached wires in the battery compartment
• All known DC fuses test good
• All AC breakers appear to be good
• The battery isolation switch doesn't have a real crisp feel when rotated so I connected the two positive cables that go to it to eliminate the switch as a factor - no change
• battery cable rings on posts were a little corroded - not bad- but cleaned/brushed and re-seated
• Have wiggled every single cable connection I can find - all secure

Ideas? Suggestions?

Thanks in advance.
  • WA4HTZ's avatar
    WA4HTZ
    Explorer
    May 09, 2019
    There is one thing that no one has mentioned. The colored plastic sleeves on crimp terminals indicates the size wire they are to be used with, and has nothing to do with polarity. Small red is 18 - 22 ga., blue is 14 - 16 ga., yellow is 12 - 10 ga., and large red is 8 ga. (may also be for 6 ga. - not sure on that). If you don't know this, the red ones can be very confusing,

    Good job on troubleshooting and I'm glad you didn't let out the magic smoke.

    Ken
  • naturist's avatar
    naturist
    Nomad
    May 09, 2019
    Glad to hear you found the problem and were able to fix it, and especially that the cost to do so was low.

    I'm sure you've heard the phrase "trust, but verify." This applies to a LOT of things, electrical wiring included. We certainly trust that all those nameless/faceless electricians who came before us paid attention to the norms of color coding wires. Wisdom counsels we check behind them with a volt meter before we commit our precious equipment and especially our lives to their doing so. Just a word of advice for future adventures in electricity (and other things).
  • BFL13's avatar
    BFL13
    Explorer II
    May 08, 2019
    Good report! With the bit of red on a white wire terminal(see that a lot with RVs I have had), not so bad. But with a bit of red on a black wire, where black is neg, very confusing!

    I like to add my own red tape on positive wires to help with that.

    RVing is fun if you don't weaken. :)
  • wnjj's avatar
    wnjj
    Explorer II
    May 08, 2019
    Glad you got it fixed. I'd cut the red plastic part off to prevent a future recurrence.
  • alienbogey's avatar
    alienbogey
    Explorer
    May 08, 2019
    So, not long after posting I figured it out.

    The ring terminal of the ground wire coming from the water heater has a red plastic insulator. The battery guy forgot that it was a ground, got fooled by the red, and hooked it to positive. Looking at the wiring to the batteries I, too, saw the red of the ring terminal and thought it was positive.

    After a while I decided to get back to basics because the camper left with old batteries and a working DC system, and came back with new batteries, an inoperable DC, and the installer had only touched the parallel wiring of the batteries.

    I traced the red-ringed cable, realized it was a ground, switched it to negative, and voila.

    Thanks for the replies.
  • wnjj's avatar
    wnjj
    Explorer II
    May 08, 2019
    If you have 12V at the batteries, keep moving down the line toward the load center until you don't. There has to be a bad connection or blown fuse.

    Are you sure the batteries weren't hooked up with pos/neg reversed?
  • cavie's avatar
    cavie
    Explorer
    May 08, 2019
    Look at your 12 volt fuse block at the converter. There are 2 or 3 30 amp reverse polarity fuses. There is also a resettable FUSE within 6' of the positive post of the battery. Check the battery connections for correct connections.

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