Battery hook-up wrong

Discussion in '1998 - 2011 Ford Ranger' started by rwb2356, Aug 20, 2017.

  1. rwb2356

    rwb2356 New Member

    Hello my name is Bud and I live in San Antonio, Texas. I have a 1998 Ford Ranger XLT 3.0 6cyc. 4WD. I recently had to buy a new battery. When I connected the new battery I didn't realize the polarity was reversed. I quickly disconnected the battery and connected it the correct way. Truck started right up and I drove it home. A couple of days later I noticed the battery charging gauge showed battery almost dead and the battery warning light was on. I am afraid I seem to have damaged the electrical system. I would appreciate any help or advice I can get to correct my screw up. Thank-you.
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  3. ZappyBear

    ZappyBear Member

    Check the voltage at the alternator. The alternator has diodes in it that might have blown or shorted when it was hooked up backwards. The computer is still good as obviously it runs, and it has a protective diode in the engine compartment fuse box. On my '93 4.0L the alternator fuse was a 20 amp miniblade fuse in the fuse box in the engine compartment. Check all those fuses and replace the blown ones. If the alternator one blows again assuming it's blown, the alternator diodes/rectifier might have shorted.
  4. DeanMk

    DeanMk Member


    You must've had to really shove hard to get that negative wire to fit over the positive terminal post on the battery.
    The positive post on any car battery is larger than the negative one, and the ends are also sized accordingly.
    ...anyway, on with a little diagnosis suggestion...
    First, clean the battery posts and the ends that attach to them with a battery brush.
    Put a trickle charger on the battery and leave it for most of the day (when the amps reach "0", the battery should be charged. If your charger has a tester in it, use it to be sure).
    Once you have a "good" battery, start the truck and have someone hold the engine rpm at around 2500 rpm.
    Take a volt meter, put the end on the proper polarity terminal and read what the gauge says.
    IIRC, the voltage should read between 12.6 - 13.2 volts.
    If its lower than 12.6, you have bad brushes in the alternator.
    If its higher than 13.2, you have bad diodes in the alternator.
    ....that's an old quick and dirty test for alternator condition (because a drained battery could be due to an alternator not putting out).
    If the battery simply won't charge up, you have a shorted out battery.
    You can replace brushes and diodes in the alternator, if you're crafty enough, but a shorted battery can only be replaced with a new battery.


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