Topic: Temperature gauge with tach

[SCJSTU]

Why is there a difference in gauge w/o a tach?

Who restores these?

Mine quick working and my mechanic says it?s the gauge as everything else checks out ok

Or who sells a reproduction one used with a tach?

[Wills70]

 Tachman was able to fix / restore as the face was melted on mine . There is no after market for this gauge. He was able to use the electronics of the amp/ oil pressure gauge - if my memory is correct-  of a non tach cluster to use in temp gauge , so if you have any extra gauges can help with repair cost
Or  there is a NOS gauge on e bay for $500 - Sorry this was fuel guage with tach
Good luck

[Rob6648]

 I have the same problem with a 70 Mach 1 with tach. Seems like you could take the available w/o tach gauge and use it to replace the wire windings. I'm asking, dose anybody know if there is a difference in the windings? Before I attempt a rebuild I would like to hear from the voices of experience. Thanks, also I have purchased a genuine Motorcraft sending unit and will replace my Standard (China). My gauge suddenly started pegging hot hot. Engine is cool, and I have tried three adjustable potentiometers 25/50/100. They all move the gauge, but you cannot adjust it to the middle. It's either hot or cold. Any thoughts?

[RoyceP]

The sending unit is a thermister. Potentiometers work linearly so if you were to adjust a potentiometer to make the gauge read the correct temperature at any specific point it would be wrong at any other point.


You need to either use the original sending unit or one that is at least 30 - 40 years old. Modern ones made by Motorcraft or the ones from the part store are not the correct value. All of them that I am aware of will result in overheating indicated when none is happening.

[Bob Gaines]

I have the same problem with a 70 Mach 1 with tach. Seems like you could take the available w/o tach gauge and use it to replace the wire windings. I'm asking, dose anybody know if there is a difference in the windings? Before I attempt a rebuild I would like to hear from the voices of experience. Thanks, also I have purchased a genuine Motorcraft sending unit and will replace my Standard (China). My gauge suddenly started pegging hot hot. Engine is cool, and I have tried three adjustable potentiometers 25/50/100. They all move the gauge, but you cannot adjust it to the middle. It's either hot or cold. Any thoughts?

I am not saying this is the cause but it is something to check. The pegging of the gauge could indicate a dead short or grounding out of the internals of the sender. It could also mean the sender wire to the gauge is grounding out somewhere on its way to the gauge.

[hopey]

Rob6648
The wrong sender (ie aftermarket replacements) nearly always cause the gauge to read high. Get the correct one for your vehicle, they have color coded insulators over the years (red, green, white, black, clear) and easily identifiable. Here is the page from 1975 MPC to help you confirm the correct one.

[Rob6648]

Gentlemen, thank you for your replies. Here is what I have found. I thought my gauge was faulty, but it did turn out to be the sending unit. I bought a genuine motorcraft sending unit and the gauge returned to normal. Be aware, there does seem to be a few different motorcraft sending units. One for a gauge and one for a light. The threaded shaft in the top of the sending unit is different. Your wiring harness will have either a large or small connector to fit down on the sending unit threaded shaft. Actually either one will work fine, I mistakenly bought the one for a light, and it operates my gauge perfectly, but you may have to adjust your wiring harness connector to which ever one you buy.