Dancing RPM needle

[headlights]

Dancing RPM needle. Just put car back on road after 4weeks, changed ignition leads and plug extensions, rpm needle now dances around actual rpm +/- 400 rpm, and looks like it under-reads some of the time. Is this just coincidence? Engine running perfectly. Any ideas ??

[2 sheds]

Yep this can happen, i think you'll need to change to rev counter, speak to Richard at Peninsula 01884 35341 as they had a car doing just this a couple of weeks ago it only started after fitting new ignition components which seemed to enhance a possible excisting fault & and they sorted it by replacing the counter.
Tim

[cockers]

2 sheds said: Yep this can happen, i think you'll need to change to rev counter, speak to Richard at Peninsula 01884 35341 as they had a car doing just this a couple of weeks ago it only started after fitting new ignition components which seemed to enhance a possible excisting fault & and they sorted it by replacing the counter.
Tim

A cheaper solution is to get used to it.

[Bob C]

Might also be the sender unit which picks up on a castellated ring on the diff

[mrt1040]

Mine just started doing this after i fitted new HT leads (8mm Magnecor). Only does it when its ticking over.

Mark

[vroom]

The early chim rev counter is very susceptable to noise pick-up.

New leads on my Chim cured the problem mentioned.

[squirrelz]

My rev counter is undamped.
Rev it then let the revs fall and it bounces up and down for a while

[zippy500]

Mine used to do that, you havent disconnected the battery recently have you, I did, the needle danced around for a few hundred miles then after the ECU had settled down no more bouncy needle.

[squirrelz]

Its done it since I got the car (nearly a year), so I doubt it's going to settle down

[vroom]

Good one is to switch the engine off with heater motor running. reve counter & speedo go full scale before returning to zero.

Back EMF in heater motor causes that I reckon (for you technical sorts).

[headlights]

Thanks for all the replies. The Rev counter is in the post to Peninsula, They recon the problem is circuit board in the rev counter. Should get it back end of next week. Watch this space!. Has anyone changed the clock for a volt meter? thought I might do it while the dash in in bits.

[griff2be]

Bob C said: Might also be the sender unit which picks up on a castellated ring on the diff

That's the road speed sensor which drives the speedo and also put a signal into the ECU. It doesn't drive the rev counter.

[shpub]

headlights said: Thanks for all the replies. The Rev counter is in the post to Peninsula, They recon the problem is circuit board in the rev counter. Should get it back end of next week. Watch this space!. Has anyone changed the clock for a volt meter? thought I might do it while the dash in in bits.

Isn't fitting a Griffith voltmeter to a Chimaera an offence punishable by transportation to Australia?

Easy to do. Don't use the clock live feed as that is on all the time.

Steve
www.tvrbooks.co.uk