Dead Battery current leak

Discussion in 'General Motoring' started by Jeremy, Jul 1, 2004.

  1. Jeremy

    Jeremy Guest

    So I had this electrical problem. Last May at 52,000 miles. The battery
    spontaneously died while at a baseball game. My wife insisted she hadn't
    left any lights on. We had the car towed home. The alternator tested good.
    We replaced the battery and did not have a problem for another year.

    Last week at 60,000 miles, I drove the car home from a restaurant, stopped
    at the store for ten minutes, and when I came out the battery was super
    dead. Usually if the battery is dead, it clicks when you try to start it. It
    was so dead, it clicked when I turned it to 'on'. When I turned it to start,
    it went all black, no dash lights, no radio, nothing. I was able to drive it
    home after I got a jump.

    I tried to have the alternator tested, but the tool was broken at the shop,
    and my good multimeter was loaned out. So, I decided (against better
    judgement) to replace the alternator, even though I hadn't proved it was
    bad. After about two hours of replacing the alternator (first time, $120, 2
    hours labor) and the battery (second time, 30$.5 hour labor), and it was
    still draining the battery according to a volt meter.

    So I finally broke out the meter and tested the battery for current with the
    key off, and Voilla!! there was current, so I pulled the fuses starting with
    the 30's until I got to the cooling fan fuse. It turns out there was a .1
    amp short from the coolant fan fuse to chassis ground in the main fuse block
    in the engine compartment that was sucking down the juice. I pulled the
    fan relay, which disconnects all wiring outside the block and the ground was
    still there. Which meant that the short was inside the block.

    I disconnected the battery and sprayed the block with electrical cleaner and
    it appears to be working normally now.

    There is still a ground but it's only 5 milliamps. so using the battery
    mumbo jumbo calc of drain times time =amphours. It should take the battery
    about 100,000 hours to discharge. Well, it should be fine for up to a week
    at least.

    I was wondering if anyone else has seen problems with wierd shorts in the
    main fuse box.
    Jeremy, Jul 1, 2004
  2. Jeremy

    Oppie Guest

    One possible problem might be from road salt that found its way onto the
    power connections. Dry salt is not a problem but when it gets damp or even
    in high humidity, it can let currents flow. This also causes corrosion which
    is the best indicator of where the problem is.

    If this is the case, clean off with a brush as much as you can and flush
    with copious ammounts of clean (preferably de-ionized) water. Let it dry and
    spray with a waterproofing silicone after verifying that the leakage current
    is no longer flowing.

    ps - what you describe is a leakage current, not a short.

    Hope this helps
    Oppie, Jul 1, 2004
  3. If this is the case, clean off with a brush as much as you can and flush
    Sorry if this is a dumb question, but what (if any) is the difference
    between distilled water and de-ionized water? Where do you get
    de-ionized water?

    I understand the purpose - it is the ions in the water (ie, NaCl), not
    the water alone, that allows current to flow.

    richard hornsby, Jul 1, 2004
  4. Jeremy

    Oppie Guest

    Actually distilled and deionized are the same for this purpose.

    Distilled is boiled off and condensed leaving any ionic contamination
    behind. (for biological applications, distilled is also preferable as it is

    Deionized is usually made by a reverse osmosis (RO) process. We had such a
    system in our lab. With new columns we got 20 meg ohms per centimeter (a
    measure of conductivity. The higher the number, the less ionic content). We
    replaced the columns when the conductivity dropped to 10 meg ohms/ cm.

    Where do you get it is another matter. If you have an up-scale home with a
    RO filtration system, you are all set. A 'water softener' is not the same
    thing. These actually wind up adding some salt to the water (as I recall).
    Otherwise you can usually buy distilled or deionized water at the

    Oppie, Jul 1, 2004
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