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MG MGB Technical - ignition light STILL on,

I have installed a NEW generator, a NEW voltage regulator and recharged the battery in my 1965 mgb and the ignition light is STILL ON. The electronic Tach needle drops to zero when i rev the engine ( The car was converted to negative ground 17 years ago ) I have restored my car 18 years ago and have NEVER had this problem.......I'm all ears fellow MGers....

aaron
aaron

Aaron - Did you polarize the new generator when you installed it? If not, you could be putting out the wrong polarity voltage. Also have you rechecked the wiring for about the umpteenth time since replacing the generator and regulator. I would suggest, what we used to call a hand over hand check - disconnect both ends of each wire in turn and checking that there is continuity, or physically trace the wire from one end to the other to insure that everything is connected correctly. If you checked the wiring with an ohmeter without disconnecting both ends of the wire, there are sneak paths that can lead you down the garden path. Good luck - Dave
David DuBois

Double-check the generator/dynamo - once correctly polarised - by disconnecting the wires from its terminals, connecting the two terminals together and to a 20v voltmeter. Start the engine - DON'T rev it!! - just slowly increase the revs watching the voltmeter. It should get to 20v by the time you get to 1000 rpm. DON'T exceed 20v. If that checks out reconnect the wires to the dynamo with the voltmeter on the D terminal (brown/yellow wire) and again start up and slowly increase the revs watching the voltmeter. The voltage should rise then stabilise at about 14.5v, it it goes higher again don't let it go over 20v. If it stabilises at 14.5v it is charging OK but I guess it won't be. If the D terminal shows only about 1v there is a disconnection in either the brown/yellow or the brown/green between dynamo and control box, or a fault inside the control box.
Paul Hunt

This thread was discussed on 18/01/2003

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