I'm sure this has probably been asked B4.............

Warning light glows brighter with engine speed. Goes out at around 800 rpm, then comes on again at low idle, say 500 rpm.

Just spent (wasted?) the whole day overhaulin' my 15AC alternator. It charges great, but that little red light is beginning to annoy me. Alternator is one of those (rare?) 4 terminal jobs, circa 1969 which uses the 4TR external regulator.

Any suggestions would be appreeeeeeeeciated. Thanks

Connections clean - including the regulator?

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

OK at the alternator end Dave, but I'll have a fiddle with the regulator.

Those little back boxes tend to worry me.

The warning light glows when there is a difference in the potential on either side of it.

This can happen when something fails completely and it will then glow brightly.

It can also happen when there is a high resistance joint somewhere, this is what your problem sounds like which is why wombat asked if connections are clean.

Basically what is happening is at low revs there is a difference with the output being low, when revs increase a bit everything is equal so the light goes out, increase revs more and the output goes higher creating another potential difference causing the light to glow again.

You need to check all connections are clean, tight and in good mechanical condition. When this happened to me it was the large spade connector on the solenoid, it had fractured but was still contacting and things were working.

Hope this helps

Cheers
Steve

Check the pulley retaining nut is tight.
If it is loose, the alternator light will get brighter with increased RPM.

Well, it turned out to be one of the diodes in the diode pack. Thought I'd checked it, but probably overheated one of the little buggers when re-soldering. Anyway, problem fixed & thanks for everyone's tips.

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1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.