Rev counter temperamental?

[Speedy88]

Hey guys, seems like a silly question this but how does the rev counter work? I guess it's electrical as theres no cable like the speedo. If it is electrical, where does the signal come from to tell it how far to move?

Reason I ask is the counter has been really really dodgy lately, just working when it wants to. I'm thinking possible loose connector but which connector should I be looking at?

Cheers and for your trouble, pics:

[Ride_on]

They are usually electrical and trigger from the coil low tension side, basically integrating the pulses to give a frequency to voltage conversion.

The usual reason for erratic behaviour is a poor connection, in my case I had a problem with the battery earth strap (360) as it wasn't bolted to the body properly. With a BMW it was the +ve alternator connection loose, both cause erratic rev counters.

[pettaw]

Yup, the rev counter triggers from the ignition coil low side/Renix unit. It could well be a dodgy dash connection, the connectors under the dash are notorious for going a bit iffy, and need a good dose of contact cleaner once in a while.

[volvosneverdie]

*Im deleting this post as it was written by an idiot that confused a rev counter with a speedo.*

[magnumpi]

I've been in the dodgy dashboard club for months now, it idles at 250rpm and at full chat it goes all the way up to the heady heights of 1500rpm

I've tried all my connectors dash end and it made no difference so i just accept it doesn't work anymore

[volvosneverdie]

I've been in the dodgy dashboard club for months now, it idles at 250rpm and at full chat it goes all the way up to the heady heights of 1500rpm

I've tried all my connectors dash end and it made no difference so i just accept it doesn't work anymore

Dear Magnumpies rev counter.
Youre not doing it right.
Please count more revs.

[theo2468]

a pulse is sent up to the dash by the renix and i believe it is the grey wire have a little check down that end aswell

[Chris_C]

As we already know you have dodgy fusebox connectors dude, I'll put money on you having a bad earth on the dash cluster. I also put a teeny bet on your flexi pcb having a burnt out track on it when you look into it, in the course of bad earths I've seen the car try and earth everything through the rev counter before, loads of scrappy dashes I've had have had a burnt track.

[Speedy88]

I've deffinatly got bad earths. The radio for one gets red hot sometimes as well as the ignition barrel Nothing like a red hot car key for your pocket.

[Chris_C]

FFS. Right, this is your problem

Is this going to be a case of bringing it here and us both swearing at it for a day?

[volvosneverdie]

Is this going to be a case of bringing it here and us both swearing at it for a day?

Ahem,

......................... then yous can fix the car.

[Speedy88]

FFS. Right, this is your problem

Is this going to be a case of bringing it here and us both swearing at it for a day?

Possible. I have had this problem since forever though