Speedo / Tach / Gauges: How to Bench Test Temperature Gauge

[mjeansonne]

My 62 Hawk temperature gauge is registering 210 to 240 degrees F after the engine is warmed up. A digital thermometer indicates only 180 F at the same time. How can I check the Temperature Gauge for accuracy? Then, how can I adjust it if its not accurate?

[jlmccuan]

Is your digital thermometer sensing at the rear of the head or in the radiator? A good way to bench test is to remove the sensor and place it and thermometer into a pan of boiling water. Watch the gauge and thermometer as the temp in the pan cools.

[kurtruk]

Don't forget the issue of clogged waterjacket passages. If no water is circulating where the sensor is because of built-up crud, yes that is a hot spot. Bad thing. But other areas of engine are not that hot due to circulating coolant. Someone else should elaborate more on this subject. Often covered in TW Co-operator.

[mjeansonne]

Sorry, forgot to mention that we just finished putting the engine back in the car after giving it a good cleaning, inside and out (water passages, and they were dirty!!) and resealing the engine. So that's why I want to check the heat gauge... is it accurate, which I don't think so. When I find out is inaccurate, how can it be adjusted?

[jlmccuan]

Test with a known instrument in the same place and let us know what the readings were and where they were taken. Sometimes you can adjust the gauge, but the sending unit or it's connection could be the problem just as well.

[Dan Timberlake]

by digital thermometer are you referring to one of those non contact laser guided infrared things? They assume and use a standard "emissivity" of something like 0.9, which is rarely right, and very wrong for shiny surfaces and some paint too.

[Guest]

The gauge is a sealed unit and not adjustable. Make sure the gauge housing shell in the dash has a good ground. Originally Hawks only got gauge ground return through the speedometer cable jacket but by the vintage of yours there should already be a separate ground braid. But the ground connection could be oxidized. This is usually noticed by the fuel and temperature readings changing when the dash lights are turned on.

The sending units seem to fail more frequently than the gauges and aren't very expensive. The last time I had this same issue I used a known good mechanical temperature gauge which I screwed in, in place of the sender, and checked things that way. But that isn't a very practical suggestion these days as those gauges aren't too easy to find.

[pdrnec]

[jclary]

If your gauge is one of the electrical (as opposed to the Bordon tube type mechanical) ...make sure you did not use Teflon tape on the threads of the sending unit. I have read somewhere that it messes with the ground of the sending unit causing bad readings.

If you insist on a "bench" test, park the car on a bench, install a different sending unit and gauge, and test away!

[pdrnec]

A bad ground would result in a low reading, not high - more resistance = lower deflection.

[skyway]

The temp and fuel guages on my GT both rise when the headlights are on?

[t walgamuth]

Anybody know of a place that will repair the flexible tube on an old mechanical temp guage?

[jnormanh]

Anybody know of a place that will repair the flexible tube on an old mechanical temp guage?

Search the internet, there are dozens of places.

I've used these folks with excellent results

https://Www.nisonger.com

[kurtruk]

Anybody know of a place that will repair the flexible tube on an old mechanical temp guage?

Some where on this Forum there is a thread on the subject which has a link to another old car site that gives a How-To on repairing the bordon tube type yourself. Good luck.

[rkapteyn]

I have used Wolf in Ohio with good results for temperature gauge repair.
They also repair gas sending units in the gas tanks of most all Studebakers

http://www.antiqueinstrument.com/

Robert Kapteyn