Pantera DeTomaso Temperature Gauges

Over the years I have heard that the temperature gauges in Pantera’s were a bit off. And, I’ve heard that adding a 10 ohm resister in series with the temperature probe would make the gauge more accurate. In fact, at least one vendor offers a nifty plug and play setup to do just this. Our car came with the 230F gauge – which shows 160F as the centered point on the scale. With a 190F thermostat – the car always looks like it is running warm. And, when the car is actually hot – as in I set the radiator fan controller to come on at around 210 and off at 220F, well, it looks like the thing is really too hot, with the needle way over to the right. I was also aware that later cars came with 260F gauges. So, I set out to find a 260 on eBay. Sure enough, one showed up and found a new home. Naturally, I was curious how accurate it was. And, well, for that matter, how accurate the original was. Early on I tested the 230F gauge to see if the Echlin TS6628 temperature sensor would work. I set up this apparatus to see what I could learn – an aluminum container filled with water that I could heat with a heat gun, temperature sensor and temperature gauge in the water, two volt-ohm meters to see what the sensor’s resistance was, and the temperature gauge left in the dash, with the engine wires extended to the temperature sensor in the aluminum can. Oh, I used a screw driver to stir the water in the can.

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Figure 3 – Original 230F Temperature Gauge Performance

The 230F gauge is pretty accurate around 90F. But, from around 122F (50C) to 230F – it reads low by 15 to 20 degrees. As an example, the original gauge reads 230F with 14 ohm resistance across the sensor.
To show a 14 ohm resistance, the sensor has to be at just over 250F.

OK, so let’s add a 10 ohm resistor. For the gauge to read 230F the resistance across the sensor would have to be 4 ohms (14 needed for the gauge to read 230 – so, with 10 ohms from the resistor, the probe can only provide 4 ohms). Wow, now the sensor has to be up around really hot to get the gauge to read 230F.

The impact of the resistor is much greater at higher temperatures. In comparison, at 122F, the gauge needs to see 88 ohms across the sensor, which means the sensor needs to be at around 140F. Add a 10 ohm resistor and the sensor needs to be at around 145F.

Directionally, the 10 ohm resistor is not helping, but it does make the gauge display a lower temperature. Not a correct temperature, mind you, but a lower temperature.

The temperature/ohms response of the 260F eBay gauge is shown on Figure 4.

230F Temperature Gauge