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Mike S.
Mike S., Classic Car Mechanic
Category: Classic Car
Satisfied Customers: 7368
Experience:  A.S.E. certified with 25+ years experience.
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I have a 1978lincolin v 78k org.miles everything org.down to

Customer Question

I have a 1978lincolin mark v 78k org.miles everything org.down to the 8track. But something keeps draining my battery I can not figure it out no one can please help.
Submitted: 1 year ago.
Category: Classic Car
Expert:  Mike S. replied 1 year ago.

You need to test the drain on the battery, then start removing the fuse one at a time until the drain goes away or at least lower than 50 mA. If you have radio presets, a clock or anything else with memory, than may draw a little, but if it's less than 50 mA, it's ok.

What you need to do in order to test the drain is disconnect the negative battery cable and place an ammeter inline with the disconnected cable with the negative test lead on the negative battery post for correct polarity. Close all the doors, remove the key and close the hood if it has a light just enough to put out the light or remove the bulb if it has one. Then start removing the fuses one at a time and leave them out until the drain goes below 50 mA. I will assume of course the drain is above 50 mA. If you need to keep the drivers door open while pulling the fuses, just push in on the door jamb button each time you pull a fuse and look at the ammeter.

If when all the fuses are out and there is still a drain higher than 50 mA, disconnect the wires at the alternator to check that. If still, disconnect the lightswitch, cause I believe that is non fused.

Once you determine which fuse's circuit is causing the drain, hook the battery back up and see what on that circuit don't work, that might give you a clue as to where the short is, so now using a voltmeter test along that circuit for where the 12 volts suddenly gets lost and shorted. Or if everything does work, now remove that fuse and place the ammeter it that fuses socket and disconnect each item on that circuit until the ammeter drops below 50 mA and that will tell you which branch circuit it is and it might be a part that is burnt up and shorted.

Expert:  Mike S. replied 1 year ago.

Have you found which fuse it is yet?

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