1. Home
  2. Car Maintenance
  3. Corsa 1.5 td alternator

Corsa 1.5 td alternator

Hi

The rev counter on my 94 Corsa td is flickering badly and occasionally it will go all the way to red whilst doing only a bit more than ticking over. Don't know if the two events are linked but it started after I drove very fast through some water. It's been like it for a few weeks now but there's no sign of the battery not being charged. Is it possible that the alternator is ok and that the rev counter part of it is dodgy? Or is it just a matter of time till I need a whole new alternator? On one occasion I started it up and got no revs showing atall and there was a slight burning smell then the needle satrted to move. Thanks to any replies.

Jon

Reply to
Jonathan Curtis
Loading thread data ...

The message from "Jonathan Curtis" contains these words:

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

Reply to
Guy King

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

Rob Graham

Reply to
Robin 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'!

Reply to
Scott M

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

Reply to
Moray Cuthill

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

Reply to
Robin Graham

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.

*IF* it's got an ECU. Most non-bang-up-to-date diseasels don't have.
Reply to
Adrian

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.

Reply to
Guy King

Thanks. You learn something new every day.

Rob

Reply to
Robin Graham

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.