C2 temp gauge dead

[Randy S.]

My 66 temp gauge just went to "zero" ( actually all the way left around 100*). It was working this morning on my way to a show but when I stopped for gas on the way home I noticed the gauge is at 100. I tried wiggling the connector at the sender but gauge is still dead or 100*.

A quick search of the archives gives me 2 tests.

Check the sender by boing it in water and measuring the resistance. expected value around 100 ohm.

Check wiring and gauge by inserting a 40 ohm resistor between sender lead and ground and gauge should be at the high end.

A lot in the archives about not accurate readings but I could not find the "dead gauge" condition. The fuel gauge works so I don't think it is a blown fuse.

All the gauges were redone around 5 years ago so hopefully it isn't the gauge itself.


Randy

[Joe C.]

Re: C2 temp gauge dead

Remove the green wire from the sender, ground it and the gauge should peg full scale.

[Michael G.]

Re: C2 temp gauge dead

Remove the green wire from the sender, ground it and the gauge should peg full scale.

Randy,

Let me expound on what Joe had to allow. Once you've grounded the green wire at the sender denote gauges action. Should gauge go full scale as Joe has suggested, gauge should be ok and you have a bad sender. If not, more than likely a gauge issue. I would bet your sender has went bad.

[Randy S.]

Re: C2 temp gauge dead

Remove the green wire from the sender, ground it and the gauge should peg full scale.

Joe,

That was it. bad sender. I clipped a jumper between ground and the sender wire then tried to just momentarily turn the key. The gauge not only pegged but went around to about 5 o'clock!!!!

Hooking it back up normal returned the gauge to 100*. I located a Standard ST-6 sender and installed it and everything seems fine. With engine warmed the gauge is at the line between 100* and 210* and IR gun says 170*

Close enough

Thanks for the help

Randy

[Joe C.]

Re: C2 temp gauge dead

Randy,

Here is a reasonable interpretation of how the temp gauge hash marks should have been labeled. Interpolation shows the non-linearity of the gauge readings, and that the sensitivity decreases as engine temps increase (readings become more compressed as temps increase).

[Joe R.]

Re: C2 temp gauge dead

Randy,

Here is a reasonable interpretation of how the temp gauge hash marks should have been labeled. Interpolation shows the non-linearity of the gauge readings, and that the sensitivity decreases as engine temps increase (readings become more compressed as temps increase).

Joe,

Is that temperature in Farenheit on top with resistance in Ohms on the bottom? The engineer in me is coming out again!

Joe

[Ken A.]

Re: C2 temp gauge dead

Gentlemen, according to our GM print, 180 degrees equates to 105 ohms of resistance. The thermistor is designed on a hyperbolic curve, rather than a straight line.

[Joe C.]

Re: C2 temp gauge dead

Joe,

Is that temperature in Farenheit on top with resistance in Ohms on the bottom? The engineer in me is coming out again!

Joe

The upper numbers are temps, in degrees Fahrenheit.
The lower numbers are the "deltas" between each hash mark, in degrees Fahrenheit. You see how the deltas get shorter as you move to the left.

[Joe R.]

Re: C2 temp gauge dead

The upper numbers are temps, in degrees Fahrenheit.
The lower numbers are the "deltas" between each hash mark, in degrees Fahrenheit. You see how the deltas get shorter as you move to the left.

Joe,

Ah, I see. That complicated math we call subtraction.

Joe