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MG MGB Technical - Pulsating Electrics

My lights (headlights, dash lights, etc) pulsate at any engine speed above about 2000 rpm. The alternator is new and was checked and verified to be operating correctly. The battery stays fully charged. Any ideas as to the caused? Thanks!
Bob Stafford

Bob- Paul Hunt is the electro-guru. I'd suggest taking your thread below to "electrical Problems etc". Paul seems to always be lurking there, ready to give away valuable nuggets, always spot on.
vem myers

Hi

We seem to be having an epidemic of alternator probs from US contributors.

If the problem started when the new alternator was fitted, I would strongly suspect that it (the new alternator) is the problem, despite the bench tests.

Why was the alternator replaced ?.

It may be worth checking for dodgy wiring connections in the alternator / starter motor / battery region.
It might also be worth checking that the alternator body is grounded to the block, and that the block to chassis strap is in good order.

My suggestion for any suspected alternator problem is to get a spare alternator from the breakers, establish that it works OK and try substitution testing. The spare should, of course, be one that fits without changing brackets, connectors, etc.
The spare alternator can also be used to 'tide you over' if your fitted alternator fails and you can't get a new one immediately.

Don
Don

My experience with this curious problem was with an original, 33 year old Lucas 16ACR with 78,000 miles. Namely, it was worn out.
I believe Paul Hunt in one of his informative posts indicated that when the brushes are badly worn this "flickering" will occur in the 2000-2500 rpm range. On mine the flicker would be gone at rpms greater than 3000, but return at intermediate speeds, and not be present at idle. The battery charged fine, and the ignition light never came on.
There was also a curious whine or whistling in the same rpm range, especially at night with the added load of lights, fan motoer etc.
A rebuilt 18 ACR cured the problems.
Andrew Blackley

Hi

I guess that new brushes sticking in their holders might have the effect described by Andrew.

Don
Don

This thread was discussed between 12/10/2003 and 13/10/2003

MG MGB Technical index

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