Alternator?

Rev counter picks up it's signal from the alternator. I'd suspect your new alternator. If it's under warantee then take it back. If not then I got mine rebuilt for around £35 at a rebuilder (ring a local auto elctrican they should point you in the right direction). Auto sparky won't be cheap.

Lee D

On or around Thu, 19 Jan 2006 17:39:27 GMT, "Dale Clarke" enlightened us thusly:

check the belt is OK. Check connections on the back of the alternator. If these are all sound, then hunt the receipt 'cos the alternator is dud.

If it's a 200TDi, then it sounds like a slack belt.

Oh, and check the earth strap on the alternator and the alternator mounting for security.

Good stuff but if the basic power system of the vehicle was stuffed I'd expect more than just the battery light and rev counter playing silly Bs. What happens when you turn the headlights on during tickover then rev up is there a noticeable increase in brightness? When ticking over and you put the heated rear screen on does the engine note/revs change?

How "electronic" is the rev counter? Is there a dodgey multiplug on/in the dash wiring?

...and Lee_D spake unto the tribes of Usenet, saying...

Remove, clean and make secure the wire to the back of the alt (terminal W?) first - that's where the rev counter picks up the signal, and these wires often corrode and get loose. Alternator itself could be fine.

"Dale Clarke" ha scritto nel messaggio news:j9Qzf.2852

These are sign of sloppy cabling from the new alternator. I had same problems with mine, when "it was young". Had to tighten cable fixing nuts beyond specs, in order to have the rpm counter give stable readings. give it a try.

"Dave Liquorice" ha scritto nel messaggio

Fully, it has a servo motor who actuates an indicator needle, and responds to a train of pulses coming from the alternator.

The faster the engine is running, the more frequent the pulses, the greater the angular deviation of the needle. Any instability of the indicator comes from the train of pulses not coming in regularly, possbly from a wimpy connection.

I even purchased a spare rev counter before eventually fixing the cable issue.

As for lights brightening when engine revs up: this comes from a less-than-fully charged battery. At low revs it is the battery who feeds the lights (say, at 11 V). When the engine revs up, the alternator puts out a full 14 V - they are fed to the battery and to the lights, inversely to the internal resistance of battery and lights. The lights now get a higher tension and brighten up.

I second that. I had major problems with strange rev counter readings, and after 4 attempts, dealer finally replaced spade connector on alternator cable. No problems since then.

Cheers! Graham

I live an learn.

Well a properly working alternator will and one without any relatively high impedance bits in it's wiring. If the lights don't brighten with revs I'd be concerned that the alternator or its wiring has something not quite right with it. Hence suggesting it as a basic test.

The step in brightness on the DII on a cold dark morning in full defrost mode and full lights is quite hefty and doesn't happen until something over 2000rpm. First time it did it I thought I was seeing things... That is a pretty cruel test though, with heated rear and front screens on (2 x 45A of fuses for the front screen), the blower flat out and main beam.

In article , Graham Carter writes

Indeed, and not just that but also check the earthing, to the instrument cluster as well as the main strap. It may be corroded, which can make it intermittent and/or add noise which will cause funnies.

Regards,

Simonm.