My tach and temp gauge are not functioning when my Shelby is running

[mjv458]

With the help of two great friends, we got my Shelby fired up today. Before its two year slumber, the tach and temp gauge worked fine. Now when it is running neither work. I let the car run for 20 minutes and the temp gauge never moved. Any suggestions on what the problem could be. Thanks and nothing sound better than a running GT500.

[Bob Gaines]

With the help of two great friends, we got my Shelby fired up today. Before its two year slumber, the tach and temp gauge worked fine. Now when it is running neither work. I let the car run for 20 minutes and the temp gauge never moved. Any suggestions on what the problem could be. Thanks and nothing sound better than a running GT500.

First was there any electrical changes done between last running and now like petronix etc. Make sure you have your wires correct on your engine gauge feed harness. Confirm in wiring schematic that you should already have.

[shelbydoug]

The tach has the tendency of attracting fine metallic dust and it accumulating on the jewel movement. There it fouls the movement.

It is important that it's case maintain a complete airtight seal to minimize this.

In my case it worked but would not indicate over about 1,200 rpm.

After servicing, it now works fine.

The technician asked me if it had been stored in a shop where there was a lot of machining of metal as he couldn't imagine how this could have happened otherwise.


I don't know about the temp gauge but perhaps it's the same scenario? With the temp gauge it is usually all about the sending unit being replaced with a non-Ford replacement.

[mjv458]

Thanks for the replies. No Pertronix still have my dual points.

[Bob Gaines]

Thanks for the replies. No Pertronix still have my dual points.

if you have confirmed that the wire going to the temp sender is the correct temp sender wire then ground it to the metal of the engine and turn the key on. If the gauge goes full tilt then the the gauge is fine and the sender is bad. If the gauge does nothing then that is more problematic and indicates a gauge or wiring problem. Hopefully the gauge goes full tilt because the indicates a easy fix. At least for the temp gauge.

[1175]

What about the instrument voltage regulator on back of gauge pod?  I recently replaced mine.  Not sure it would affect tach, but would affect temp gauge.

Jon