replacing the clock with a tach

[Destin H]

I'm trying to replace my clock with my new tach. this is a pic with the tach installed and the old clock wires hooked up to the bulbs, my question is, what do I do with the red wire that hooked up to the clock and the brown wire that was grounded to the back of the gauge cluster. and where to look for the third wire because there are 3 leads.

thanks

[yeewiz]

need pic!

[halboyles]

Here is the wiring diagram for the instrument cluster for '73 on.  The clock has its own connections on the instrument cluster (circled in green.)  That three pin wiring connector is not the same configuration as the three pin connector for the tach so you are going to have to get one of those harnesses.  You will find a black wire behind the instrument cluster that connects to the tach to provide the rpms.  The black wire probably connects to your condenser on the distributor.

[Destin H]

[Destin H]

On 10/11/2017 at 1:55 PM, halboyles said:

Here is the wiring diagram for the instrument cluster for '73 on.  The clock has its own connections on the instrument cluster (circled in green.)  That three pin wiring connector is not the same configuration as the three pin connector for the tach so you are going to have to get one of those harnesses.  You will find a black wire behind the instrument cluster that connects to the tach to provide the rpms.  The black wire probably connects to your condenser on the distributor.

Thanks that's really helpful In the abouve picture I was trying to use the clock wiring for the tach and they don't quite reach. Is this wiring connector something I could buy at a hardware store or hobby shop or is it one of those very specific bmw parts that you can only get from bmw?

Edited October 12, 2017 by Destin H

[Son of Marty]

Your best bet would be to post a add in the parts wanted section I'm sure someone will have one at a reasonable price.

[jimk]

10 minutes ago, Destin H said:

Is this wiring connector something I could buy at a hardware store or hobby shop or is it one of those very specific bmw parts that you can only

I can send you one from my spare cluster if you are in the US.  PM your address.

[ray_]

I'm confused. Are you replacing the tach with a clock? If not, why is the clock harness needed?

[Tsingtao_1903]

The red wire is fused, but, always on to power the clock.  The third wire is typically gray for illumination;  It is switched on by the panel light switch.  The brown wire is return for both the red and the gray wires.  If you use the clock harness to power your tach, cap the red wire and secure it as you don't want for it to short to anything.  Use the gray wire for switch power.

[Destin H]

so I found the wire set for the tach and the back of my instrument cluster looks just like the picture provided by halboyles at the top, all I need now is to find this black wire. does it connect to the capacitor that's mounted on the side of the distributor or does it come from somewhere else. Pics would be appreciated.

 

[Destin H]

I mean the black wire that connects the ignition to the center lead on the back of the tach.

[halboyles]

There should be factory wiring on the firewall behind the distributor that splits up and goes to the condenser on the distributor and the #1 terminal on the coil.  You can check continuity between the two ends to make sure you have the correct wire.  That black wire goes to the back of the instrument cluster and also to the diagnostic plug near the fuse box.

 

Here's the distributor/coil wiring.

[HBChris]

I put a tach in my 75 and the black wire was already there behind the instruments, yes, it goes the to the condenser on the dizzy.  On early cars it went to the coil.

[halboyles]

6 minutes ago, HBChris said:

he black wire was already there behind the instruments

That was true on my '71 1600 as well.

[Destin H]

I was looking for one on mine but I guess they just didn't put the tach wire in the cars that had clocks in 1968? Any way, thanks for your help guys I just ran a wire from the condenser to the middle lead on the  tach and it works great 

Edited October 12, 2017 by Destin H