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MG MGA - Alternator/ignition light

Has anyone who has fitted an alternator to the MGA ever connected a new wire directly to the ignition light rather than the usual method of using the (bypassed) original control box as a connector?

I have had issues with the ignition light glowing slightly, intermittently since I first fitted the alternator 4 years ago.
It has always charged the battery perfectly and its output voltage has always been in the region of 14v and so I have not been too concerned.

But I am planning a long trip in a couple of months and I have decided to swap the alternator for a reconditioned one to make sure everything is up to scratch.

My thinking is that with a new wire fitted direct to the ignition light instead of through the original loom I can then rule out any spurious voltages getting to the light which may have been causing it to glow a little.

I will also connect the other side of the lamp to a new earth to complete the wiring.


c firth

Those lights are just that. I would consider i9nstalling a voltmeter and then you can see what is actually happening.

Not MG but I had a new 1959 Chevrolet with those idiot lights. It glowed when it felt like it. I sold the car at 150.000 miles and it was still glowing.
ss sanders

Yes, you can connect directly to the ignition lamp.

When installing an alternator with internal regulator, you have to switch some wire on the original control box to bypass function of the control box. You can just as well remove the original control box all together. In fact, if you do not remove the old control box, it is possible under some circumstances for the old box to interfere.

Specifically, the old box may have the cut-out relay contacts stick closed so the ignition light remains on after shut-down. You can isolate the contacts with a bit of insulating material in between the contacts. Or you can cut the conductors inside the control box. Or you can remove the control box.

See here:
Barney Gaylord

Thanks Sandy, thats good to know.

Barney, thanks for the info,
I did get the problem with the cut-out closing when I switched the ignition off and I fixed it by sliding some plastic shims in between the contact points which solved it.
I don't know why I retained the control box for the sake of originality when I had already stuck an obviously non-standard alternator on the engine!

I will fit a the new wire to the lamp and let you know how it goes.


c firth

This thread was discussed between 15/04/2014 and 16/04/2014

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