Corsa 1.5 td alternator

The message from "Jonathan Curtis" contains these words:

Sounds more like a loose connection on the back of the alternator.

Does the alternator have something to do with the rev counter, then?

Rob Graham

On Diesels, yes. Trad petrol systems counted the number of sparks to calculate revs and you obviously can't do this in a Diesel so they measure via the alternator. Not sure how tho'!

They take a signal from the alternators AC output before it get's rectified, and use it to drive the rev counter.

No. I wonder how, given that alternators are untoothed belt driven. Are you sure they don't do it via the ECU which must take note of the revs.

Rob

Robin Graham ( snipped-for-privacy@btinternet.com) gurgled happily, sounding much like they were saying :

Assuming the alternator isn't slipping - which isn't *that* often - there's a linear relationship between revs and alternator revolutions, which directly equates to the unrectified alternator output frequency.

The message from "Robin Graham" contains these words:

Yes, being a diesel there's no ignition circuit to derive the pulses from, so it picks up a signal from the alternator instead.

Thanks. You learn something new every day.

Rob