Got a bit of a strange one here, upon driving the other day I noticed my alternator was playing up as my dials were dancing about and the lights were pretty dim. Managed to get home though.

The next day I tried starting and obviously it wouldn't turn over so I jump started it and got the multimeter out. With the engine off I could see 12v at the terminals. With the ignition on I saw 12v at the small wire for the alternator. With the engine running I'm seeing 14v across the terminals.

I decided to buy a proper volt meter gauge and wire that in, same results however when I go above 2000 rpm the alternator seems to stop charging.
Any ideas on what to look for next? Kind of tired having to accelerate to speed then coast as far as possible

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Goldie the track car.

Thanks Rich, i can't see it being the belt slipping as its an 8 rib one and the supercharger is still supplying full boost when i want it to, i'd have thought that would slip too if the alternator was.

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Goldie the track car.

It seems to have got worse the last couple of days, now not charging above 1,750rpm.
The electrics on the car are pretty minimal with it being a track car, even with everything turned off the voltage drops when i slowly take it above 1,750rpm so i suspect its the alternator itself.

I've bought a second hand one so when that arrives tomorrow i'll hopefully get it fitted and see if that resolves the issue.

EDIT: Cheers for the input by the way guys

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Goldie the track car.