Alternator light keeps coming on.

Hi all, got a bit of a weird one, alternator light came on a couple times on start up a week or so between each instance, when it stayed on if you gave it a quick rev it would go out.....pretty typical of a regulator starting to give trouble, so after comfirming with my auto sparky i got him to rebuild alternator, new bearings, brushes and regulator....and weld up the clutch that was starting to slip. Last fri morn ran down got some boat fuel came home messed around for half a hr then went out to start it to go to work and the mongrel light came back on. then came on again fri arvo after got home and started again after letting sit for half a hr. sun morn started it 3 times in a row from cold and light came on, took it to auto sparky yesty and he spent all day starting it, testing and checking and rechecking everything, testing every scerario and possibilty and the light didnt come on once. only other symptom it has is twice while the light has been on it started, dropped back to normal idle then cld swear heard a click or thump under bonnet and it started to idle higher than normal, perfectly steady, give it quick rev and alt light goes out and returns to normal idle..............can anyone help or come up with a possibility??????
cheers and thanks in advance

Check the earths.

My idle use to rise under heavy electrical load. Ie as in the fan on setting 4.

Clean the earths from the negative terminal to the engine and even the one that goes to the skirt.

Clean the threads and see how you go.

Fixed mine.

My 2004 D22 has the alt light come on most cold starts. The output is about 11.69v. A rev up to 1700 puts the light out and the output is about 12.7v at idle. Light very rarely comes on with warm start and never comes back on during running. Basically it is just not putting out enough sometimes at cold idle so registers a fault.

Goldie

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Krafty wears dresses, needed 10 characters.

Goldie, sounds very similar to what mines doing, same year model too lol. didnt do it for 2 weeks and then fri arvo i started it up at work and it did it. but you can tell when it is going to do it even before motor starts because if you watch the dash as motor cranks the alternator light goes out just before motor starts, so the light is already on split second before it starts, i give up lol. only difference is even before i got alternator rebuilt it was still charging 14.2 at idle and 13.5 at idle with lights etc on so i just ignore it!
cheers dan

Dave said:

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Krafty wears dresses, needed 10 characters.

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Of course I do, even when I don't see such posts, however it's nice to see admins don't get deleted for off topic comments