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Rev counter and speedo not working... any advice?

Posted: Thu Jan 25, 2018 10:27 pm
by gturner008
Having just bought a 1967 912 - I begin the journey of fixing it up. Its not been driven properly for about 10 years.

The first things I notice are the rev counter and speedo don't work. Any obvious things that might fix or to look for? I'm planning on getting the car up on a lift on the weekend to have a look. I'm guessing the speedo is a cable from the gearbox to dial? Not sure about the rev counter. Electric from sensor in gearbox to rev counter?

Many thanks

Gary

Re: Rev counter and speedo not working... any advice?

Posted: Fri Jan 26, 2018 4:16 pm
by neilbardsley
gturner008 wrote:Having just bought a 1967 912 - I begin the journey of fixing it up. Its not been driven properly for about 10 years.

The first things I notice are the rev counter and speedo don't work. Any obvious things that might fix or to look for? I'm planning on getting the car up on a lift on the weekend to have a look. I'm guessing the speedo is a cable from the gearbox to dial? Not sure about the rev counter. Electric from sensor in gearbox to rev counter?

Many thanks

Gary
"Electric from sensor in gearbox to rev counter"

I think it's a electric cable to the coil that measures frequency but I stand to be corrected. The first step I would do if put you digital rev counter onto the back of the RPM counter in the dash. That way you will know if you are getting a signal. Why you are there you can check to see if the speedo cable is connected.

Re: Rev counter and speedo not working... any advice?

Posted: Fri Jan 26, 2018 5:51 pm
by SeanP
Rev counter is triggered from the coil. Three wire on the back of the tacho 12v 0v and the trigger cable from the coil, don’t have a wiring diagram to hand. (You can find one on the web).

Speedo is driven from the gearbox. Cable siezed and snapped would be the obvious answer.

Hope that helps

Sean

Re: Rev counter and speedo not working... any advice?

Posted: Fri Jan 26, 2018 10:45 pm
by gturner008
Great advice. Very much appreciated. I’m going to have a look at this tomorrow. Best, Gary

Re: Rev counter and speedo not working... any advice?

Posted: Sat Jan 27, 2018 11:04 pm
by gturner008
For the life of me I can’t see where the speedo cable connects to the gearbox. Any clues?

Re: Rev counter and speedo not working... any advice?

Posted: Mon Jan 29, 2018 10:29 am
by Lightweight_911
The speedo drive gear is on the right side of the gearbox - when viewed from the rear of the car (just above the mounting crossmember) - close to where the gearshift rod attaches:

Image

Re: Rev counter and speedo not working... any advice?

Posted: Mon Jan 29, 2018 1:40 pm
by gturner008
Thanks Andy. I found it yesterday. The bit that spins around pushes into the housing, meaning it does not engage with the cable. I’ve pulled it outwards with pliers, and thing it pops back in. I guess I have to buy a new piece?