[Louey]

I just re-did my instrument panel, because the clock wasn't working. Now that I have everything back together, the tachometer no longer works.

I replaced the ribbon circuit board as a part of the overhaul.

It looks to me like the tach just feeds off the ribbon. I don't see how I could have done anything wrong. I don't see any other connections for the tach. What am I missing?

Where would be the best place to start looking for the problem?

I really don't want to pull the cluster again. That was a bear.

 

[RealRed70]

You probably need to tighten the nuts a little tighter on the Printed Curcuit Board that are for the tach. Two small nuts that are right next to each other on the back side of the tach. You do have the brown wire connected to the - coil terninal? To make the tach work you need these connections 12 volts + which is pin # 7 in gauge harness plug , brown wire to - coil terminal, which is pin # 9 and a grounded tach.

 

[Louey]

I'll double check the coil wire. I never disconnected it, so it shouldn't be a problem.

I'll double check the nuts too.

 

[Louey]

I couldn't find a problem with the tach wiring with the cluster installed. So I pulled it back out tonight. I must have done something wrong when I reassembled the cluster. I should have taken pictures of every nut, washer, lock washer, nylon washer, etc. when I removed it.

Here is a series of pictures that shows how it was installed. Do any of the nuts, washers etc. look out of place?

There's a bunch of pictures. I'd rather show you everything since I have no clue what I did wrong.

Here's a shot of the two nylon washer that I installed between the ribbon and the housing on the 12 volt coil posts:

Some people think a picture is worth a thousand words...

 

[RealRed70]

This is how I test tachs. With the tach removed from the gauge cluster I would connect it to the car with loose wires with alligator clips on the ends. Connect to the battery positive and the other end to the 12 volt + post on the back of the tach. Then connect the -coil post on the back of tach to the - coil terminal. Then run a wire from the negative battery terminal to the metal housung of the tach for a ground. Start the car and the tach will work if it is in working condition. If it works then you have a problem with your PCB or wire harness or you do not have a ground. Or you are not making good contact where the harness plug goes into the PCB. Let us know what you find out.

 

[Louey]

After looking around under the hood and looking through the paper work that came with the car, I found that the car has a MSD ignition (distributor cap and coil). The tach feed comes out of the bottom of the distributor on a green wire. There was a kink in the wire. It fell apart in my hands when I was fooling around with it. I stripped it back and connected it to the tach, like you mentioned above, and it works. So I have to assume that was the problem Now I have to butt splice on to the green wire to get it reconnect. There doesn't seem to be any other way to replace it. But that should work, though it's in a bitch of a place to get to.

This should fix my problem. Everything else checked out. I'll make real sure I get a good ground to the tach back plate too. Just screwing the back plate in doesn't necessarily give you a good ground, or so my meter says.

Back to the garage...