Rev counter temperamental?

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Speedy88
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Rev counter temperamental?

Post by Speedy88 » 08 Jan 2011 12:35 pm

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:

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'88 340 Williams (Sold)
'85 360 GLS - Drift project (Sold)
'77 Colt Sigma
'96 940 Drift project

Ride_on
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Re: Rev counter temperamental?

Post by Ride_on » 08 Jan 2011 03:02 pm

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.
1980 345 DL_______1987 360 GLE (project car restored to GLT spec and B230FT'd)
1984 360 GLT______1987 360 GLT
1983 360 GLS______1989 360 GLE
1985 340 GL_______1986 340 1.4
1985 360 GLS______1995 940 SE 2.3 Turbo Estate (daily)
1987 340 GL 1.7

pettaw
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Re: Rev counter temperamental?

Post by pettaw » 08 Jan 2011 04:09 pm

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
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Re: Rev counter temperamental?

Post by volvosneverdie » 08 Jan 2011 04:14 pm

*Im deleting this post as it was written by an idiot that confused a rev counter with a speedo.*
Last edited by volvosneverdie on 08 Jan 2011 05:39 pm, edited 1 time in total.
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magnumpi
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Re: Rev counter temperamental?

Post by magnumpi » 08 Jan 2011 04:20 pm

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 :lol:

I've tried all my connectors dash end and it made no difference so i just accept it doesn't work anymore :(
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volvosneverdie
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Re: Rev counter temperamental?

Post by volvosneverdie » 08 Jan 2011 04:21 pm

magnumpi wrote: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 :lol:

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.
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theo2468
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Re: Rev counter temperamental?

Post by theo2468 » 08 Jan 2011 05:24 pm

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
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Chris_C
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Re: Rev counter temperamental?

Post by Chris_C » 08 Jan 2011 06:47 pm

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.
'89(G) 340 GLE B172k
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Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast

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Speedy88
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Re: Rev counter temperamental?

Post by Speedy88 » 09 Jan 2011 01:09 am

I've deffinatly got bad earths. The radio for one gets red hot sometimes as well as the ignition barrel :shock: Nothing like a red hot car key for your pocket.
'88 340 Williams (Sold)
'85 360 GLS - Drift project (Sold)
'77 Colt Sigma
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Chris_C
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Re: Rev counter temperamental?

Post by Chris_C » 09 Jan 2011 07:00 pm

FFS. Right, this is your problem :lol:

Is this going to be a case of bringing it here and us both swearing at it for a day?
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast

volvosneverdie
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Re: Rev counter temperamental?

Post by volvosneverdie » 09 Jan 2011 07:46 pm

Chris_C wrote: 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.
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Speedy88
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Re: Rev counter temperamental?

Post by Speedy88 » 09 Jan 2011 10:03 pm

Chris_C wrote:FFS. Right, this is your problem :lol:

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 :lol:
'88 340 Williams (Sold)
'85 360 GLS - Drift project (Sold)
'77 Colt Sigma
'96 940 Drift project

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