My tach isnt working...either

[bahllr]

So I've made some headway on my 68 1600 and it is now running with brakes!

 

i need to get it running smoother and do a valve adjustment and to help dial in the idle I wanted to replace my clock with a tach.

 

i read all the posts on tach not working....I searched for the hidden black wire behind the dash and I couldn't find it. I've attached a picture to show what I see. 

 

So so I ran a black wire from the negative side of the coil through the firewall up to this location and plugged it into the center spade on a tach I swapped in. While the car is running the black wire pulses on my test light and grows brighter with revs so it seems to be feeding a signal to the tach but no movement on the dial.

 

i am wondering if my wiring could be causing an issue as my wiring loom on the back of the instrument cluster is different than those I have seen online. I don't have the green wire coming from the very far end of the dash as that port is covered with a hard foamy plastic, likely from the factory. Is this causing the issue or is it something else? 

 

i have a black wire from negative coil to tach middle prong and one to the back of the distributor. 

 

I would appreciate those with much more experience let me know if I have missed something.

 

thanks,

ben

 

[LimeySteve]

Black wire behind cluster fits empty spade on the back o d tach , it should be a flag terminal ( at 90 degrees to the wire )

[Preyupy]

the 3 terminals on the back of the tach are Ground, 12v+, and tach signal.  It looks like you don't have the 12v+ connected. 

[Simeon]

The connection at the coil looks a bit ropey too. I know it is a test but a decent crimp terminal, properly applied with the wiring run so that it won't chafe will pay dividends for reliability in the long term. 

[bahllr]

Simeon - thanks for the thoughts. I connected the red wire to the positive terminal and crimped on a spade tonight and unfortunately still had no success.

At this point I think it might be the early instrument cluster wiring (the red wire isn't hot so not sure if the tach needs power or just the signal from black) or the tach itself.


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[Preyupy]

Show us a close up of the connections on the back of the tach ( I can't remember what order they are in) you need to find a good ground and a 12v+ source. There are pins on the back if the main circuit board ( I'll look it up in the factory manual tomorrow)

[bahllr]

Prenup - thanks for the help. Here are two shots. One of the back of the tach and one of the connectors from the other side of the cluster. Seems most people have a different set of connectors coming from where I have a sealed connector...

Look forward to any thoughts.
Ben


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[Preyupy]

Does your red wire have 12v+ when the key is on? If not pull the cover off the 3 pins at the far right side of the picture of the main circuit board and check for power there. You should have 12v+ with key on, 12v+ (variable) dash light power, and ground 

[Preyupy]

By the wiring diagram I have (looks like you have the Blue Manual also) if you were to look at the 3 pin connector you have plugged into your main circuit board and call the Grey wire #1, Brown wire #2, and Red wire #3.  if  you plug it onto the 3 pins that are under the white cover.  Pin #1 would go to the + terminal on the tach, pin #2 is ground to the tach, pin #3 is the instrument lights.  You need to check pin #1 for power with the key in the run position.  There was a separate harness for the tach back in the day (the 3 pins you are currently using should have a constant 12v+ on pin #3 for the clock, did your clock work?)