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  • Engine bogs down when headlights are on.

    I have an "approximately" 1973 Mini with 998cc engine and automatic transmission. When I turn the headlights on I can hardly get up my driveway. If I turn them off, it is like a nitro boost and I zip right up the hill. I have replaced the ground between the engine and the frame and I replaced the distributer wires. The battery starts the engine just fine but is is quite small (golf cart?). I had the alternator checked (at the battery because the shop didn't have the connections to bench test it) and he said that the voltage is right at the lower limits of what he would expect but it still passed. What is the best next step:
    1. Buy a new battery?
    2. Keep looking for a ground issue?
    3. Replace the alternator?
    4. Drive up hills only during the daytime?


    Thanks in advance for your wisdom.

    Dan

  • #2
    Before you change anything check the ignition light. Does it come on with the ignition switch before you start the car?

    If the bulb fails or the connection to the ignition light fails the alternator will not charge.

    Kelley
    If you can afford the car, you can afford the manual...

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    • #3
      This doesn't make sense to me. Are you saying that a high electrical load bogs the engine? Try to isolate it with some trouble shooting-does the same thing happen when the heater fan or the windshield wipers or both are on? Disconnect the alternator and see if that cures the problem. If so, then you have your answer

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      • #4
        Do your headlights work only with the key on? The ignition and headlights should be independant of one another. If the car has been "adjusted" so the headlights (perhaps a brown/blue wire) are connected to the ignition system (those white wires) it might make the coil unhappy. Have headlight relays been installed?

        How's that for a wild guess?

        Don

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        • #5
          That's my Donnie boy, always the thinker!

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          • #6
            Sometimes I sits and thinks, sometimes I just sits.

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            • #7
              Update

              Thanks for the feedback and thinkin'.

              Ignition light comes on with the key.

              Headlights come on without the key.

              Cleaned up the connection between the battery and the frame.

              Still bogs down.

              Does not bog down with heater.

              Haven't tried disconnecting the alternator. Didn't know that was ok to do when the car is running. Do you mean, just unplug the wiring plug on the side of it?

              I welcome your ideas.

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              • #8
                A reply from the Mini Mania forum; 'Unplug the alternator (wire that goes to alternator) start the car, turn the headlights on and try the test again. That'll at least confirm if it's the alternator circuit or the headlight circuit.'

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                • #9
                  Originally posted by Jerry View Post
                  A reply from the Mini Mania forum; 'Unplug the alternator (wire that goes to alternator) start the car, turn the headlights on and try the test again. That'll at least confirm if it's the alternator circuit or the headlight circuit.'
                  Jerry, sorry for scratching my head a bit on this but are you saying that I should disconnect the wiring plug from the voltage regulator on the side of the alternator and then start the car and drive it to see if it still bogs down with the lights on?

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                  • #10
                    Yep. Just unplug it from the alternator (secure the wire bundle so it's not flopping around). The goal is to isolate/eliminate either the headlight circuit or the alternator circuit. My guess is that the car will not bog down with the alternator disconnected and the headlights on, in which case replacing the alternator should solve the problem. Fingers crossed.

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                    • #11
                      Any news??

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