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Water temp?

Ehamilton

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Oct 12, 2019
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Location
Sacramento
I’ll try to make this a quick recap. I bought a digital water temp gauge (18-255 degree) and sending unit from summit last year. The gauge started out fine (Week). Then the temp was all over the place, before settling on a max temp of 255 and never moving.
I decided to change the wiring harness, since it was on my list of thing to do and I knew it sucked.
The gauge still was stuck. I contacted summit who sent out a new gauge. However this gauge range read 22-375 degree.
Also found the sending unit was broken. For simplicity I grabbed a new one from autozone. The car now reads 140 cold (80 degree weather), 240 warm (should be about 190)
Summit is saying the gauges will sometimes go up that high. It’s normal. But my autozone sending unit is defective.
I have a feeling the temp sending unit has to mirror the gauge range to get an accurate reading and a gauge that reads 375 will never work with a sending unit built for a 255 gauge. Please help, I’m no expert
 
It very well could be the sending unit. I have the stock gauge in my 63 along with a manual aftermarket gauge. The aftermarket gauge will read in the 180* range while the factory gauge shows in the high to almost top of the scale. I checked with a hand held laser temp gun and it agrees with the aftermarket gauge.
 
I wouldn’t go mixing and matching gauges and senders. Typically they are a matched set.
 
Definitely use the pistol grip laser-sighted temp units. You can monitor temps at the thermostat housing, the sending unit, the upper and lower hoses, and all over the radiator. Works on exhaust manifolds too. Then you can double check those readings with your dash gauges.

After I paid good money for a professional gauge cluster restoration, I noticed the coolant temperature gauge did not quite reach the same spot under normal driving conditions as before the restoration. Sure enough, after double-checking with the pistol grip thermo, I verified it was reading a tad low. Good to know where one stands with these things.

thermo.jpeg
 
I’ll try to make this a quick recap. I bought a digital water temp gauge (18-255 degree) and sending unit from summit last year. The gauge started out fine (Week). Then the temp was all over the place, before settling on a max temp of 255 and never moving.
I decided to change the wiring harness, since it was on my list of thing to do and I knew it sucked.
The gauge still was stuck. I contacted summit who sent out a new gauge. However this gauge range read 22-375 degree.
Also found the sending unit was broken. For simplicity I grabbed a new one from autozone. The car now reads 140 cold (80 degree weather), 240 warm (should be about 190)
Summit is saying the gauges will sometimes go up that high. It’s normal. But my autozone sending unit is defective.
I have a feeling the temp sending unit has to mirror the gauge range to get an accurate reading and a gauge that reads 375 will never work with a sending unit built for a 255 gauge. Please help, I’m no expert
My opinion...
If your digital temperature instrument is compatible with the sensor, everything should be OK. But what sendor does the digital temp instrument need? Most, but not all, sensors are a resistive devices, whose value changes with temperature. Some sensors are positive temperature coefficient, whose resistance increases with temperature and some sensors are negative temperature coefficient, whose resistance DECREASES with temperature increase.....what does the instructions for the temperature instrument say what sensor is required? Some temperature sensors are called RTDs or Resistive Temperature Detectors but usually require 3 conductor wires to operate. To arbitrarily think that the Mopar sensor will work usually results in inaccurate readings or no readings at all. Can you supply the instructions or a diagram of your installation to accurately diagnose your problem? Maybe your instrument will require calibration to operate properly.
BOB RENTON
 
Thanks for the reply’s. I bought the sender from summit that normally works for the 255 degree max gauge and my temp seems to be right. Even through my new gauge is 375 degree max.... so I have no more problems there... still a laundry list to go! But at least the temp seems good for now
 
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