There are all kinds of temperature gauges available. Some are just look-alike repro gauges that bear only a slight resemblance to what was actually in the M38A1’s. Early M38A1’s had the Douglas connectors on the gauges and electrical system. The Douglas connector gauges, as far as I have been able to find so far, were Ordinance gauges with part numbers like 7386865.

About 1953 or so, someone put their foot down and the Mil-Spec (MS) standardization began to replace Army Ordinance, Navy NAVSHIP and BuAer and Air Force AF – parts with standardized parts for all of the military.

In later M38A1’s, panel gauges went to Mil-Spec numbers. There might be different gauge styles 0-60 PSI vs. 0-120 PSI – but a Mil-Spec for each one.

As for a temperature gauge, as I look at catalogs and pictures, the most common M38A1 gauge showing up is a gauge marked MS24543-2 (Indicator; Temperature, Electrical Resistance: 24 Volt DC, Range 120-240 degrees). Just for giggles the -2 gauge is “non-luminous”. The -1 gauge, which was been cancelled, was luminous – it had a radioactive adder to make it glow in the dark. Original R-390A radios had luminous gauges too – that’s why I glow in the dark now).

Good ol’ MS24543 only tells you that the temperature gauge “Must operate linearly and accurately when properly connected in a circuit with associated transmitter MS24537”. At least we have a gauge/sender pair we can kind of depend on.

Now, when I go to MS24537, there isn’t a lot of info there either. The spec gives three temperature/resistance points:

Cold 120-degrees F 2360-ohms (+10%, -15%)

Hot 200-Degrees F 710-ohms (+/- 5%)

Too Hot 240-degrees F 310-ohms (_+/-8%)

I’ve asked folks on this forum and the g503 to measure thee coils in the temperature and oil pressure gauges, but no luck so far.

Just from an eyeball look at the resistances in the MS chart, at about 170 degrees engine temp, the resistance of the sensor should be considerably less that 2360-ohms and a bit more than 710-ohms. It looks pretty non-linear, but your 1.1K to 1.5K might not be too far off.

What is the P/N on the face of your gauge? Is it still one of the original gauges or a repro/NOS unit?

And, that instrument panel might not be ground after you did such a good job of getting off all the rust, priming it and putting a nice coat of paint on it. You did too good a job. Sometimes you have to skin off a bit of paint to get things to work.