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  1. #1

    Default Voltage Regulator Bad?

    I had an issue with my battery on my 85 302 cfi and the alternator wasn't charging the battery. So, I got a voltage regulator from autozone and it started charging correctly, but it would drain my battery. I got a new one today, hoping it would fix some of the issues im having with my lights. My rpms wont read until I have my headlights switched. Very weird. It didn't fix anything. And I have yet to see if it drains still. Is this my regulator? Or could it be a bad connector?

  2. #2
    FEP Senior Member Tigger's Avatar
    Join Date
    May 2009
    Portland Oregon


    When I first got my 67 coupe, it had a bad drain. Alternator was new. Battery was new but if left connected it would be dead in a day or two. Connecting the battery had a large spark which was a sign that there is a large drain somewhere. I started by pulling fuse, one by one and seeing if the spark went away. It didn't make a change. I was stumped till I disconnected my voltage regulator and then the spark went away. I replaced it and the battery could stay connected without draining it.

    It sounds like you may have some other electrical issues with your car. I would take a peak behind the instrument cluster and see if you find anything that looks suspect.
    67 Mustang Coupe
    96 Tangerine GT
    86 Saleen #179

  3. #3


    When I get weird starting/charging/running issues in an early 80s to mid 90s Ford, I put "ignition switch" into my head. It's not always it, of course, but when I fix one thing and it's not really fixed...

    I have a spare ignition switch in my Fox toolbox (and another in my Panther toolbox, which is the same overall design but a different switch); it's essentially a brand new Motorcraft switch. When things get weird, I plug it in and use a small screwdriver to operate it for troubleshooting. In an emergency, I can just use that one and buy another; but Motorcraft ignition switches are one of those things that I will buy an extra of when I see them on sale cheap (also Motorcraft starter solenoids, most of the aftermarket ones are junk).

  4. #4


    sounds like multiple problems. 1) yes what you described can be a bad regulator. some last years, others weeks. to prove it use a VOM to chase the drain. or unplug the regulator when not using the car and see if the symptom goes away. i have changes a lot of them over the years. 2) when you have weird electrical symptoms the ignition switch should be a good starting spot. pull the trim off the steering column and see if the switch is coming apart. again i have changed many of these in my car.

  5. #5
    FEP Super Member gr79's Avatar
    Join Date
    Jun 2009
    SE Michigan


    Fixed a mysterious battery drain by unwrapping the entire alternator to regulator wire harness.
    Was melted in one area about at the 1/2 way point and shorting out.
    Caused by the unfused burnt out electric choke element the dealer found.
    They did not find the harness damage.
    Easy repair. Wiring, battery, charging ok ever since.
    A new Motorcraft switch (not the key cyl) is not expensive, an important wear and old age part to retire if never replaced.

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