Tachometer problem

[midlife]

Don C ,

I want to bench test the tach to make sure that the problem is in the tach before I send it out to be repaired.

Thanks,

John

No real way to bench check a tachometer, unless you have a signal generator, and even then, it may not work (you need a current generator).

 

[TheRktmn]

Under the dash:

Unplug the tach.

Install a jumper across the plug the tach came out of to complete the circuit to the coil + side.

Start the car. If it starts and runs go on to the next steps.

(this is easiest to do with the tach out, but can be done with the tach installed)

NOTE:

Coil + side is fed from the ignition switch.

Coil - side has a wire going to the distributor.

At the coil:

Remove the wire from the coil + side and attach it to the tach plug male connector.

Run a wire from the tach plug female connector to the + side of the coil.

Start the car. If it starts and runs check the tach function.

 

[midlife]

Under the dash:

  Unplug the tach.

  Install a jumper across the plug the tach came out of to complete the circuit to the coil + side.

Start the car. If it starts and runs go on to the next steps.

(this is easiest to do with the tach out, but can be done with the tach installed)

NOTE:

  Coil + side is fed from the ignition switch.

  Coil - side has a wire going to the distributor.

At the coil:

  Remove the wire from the coil + side and attach it to the tach plug male connector.

  Run a wire from the tach plug female connector to the + side of the coil.

Start the car.  If it starts and runs check the tach function.

"At the coil:

Remove the wire from the coil + side and attach it to the tach plug male connector.

Run a wire from the tach plug female connector to the + side of the coil."

This makes no sense to me.  Is there a typo perhaps?

 

[TheRktmn]

I told him how to test a tach w/o a signal or current generator.

Basically moving the tach from the middle of the circuit to the end.

We tested used tachs with this method for years. I even added a connector under the hood of my Ranchero so I could check tachs at swap meets.

 

[midlife]

Nevermind...I misread your post.

 

[Kammertime]

Thanks for all the great replies.

I went to the garage today to start on the trouble shooting tips and thought I would try the "give it a whack" solution. IT WORKED.

Is there something that needs to be oiled or sprayed to alleviate this problem ?

Thanks,

John