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TR6 Temp gauge

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airlifter

Jedi Hopeful
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The temp gauge only barely moves when operating under normal conditions.

Today I rigged up a way to check it against a known temperature. With the water boiling the gauge only went about half way over.

I checked across the sending unit at normal (4K ohms) and with water boiling (260K ohms). Does anyone know what these values should be.

i would like to determine if the problem is with the gauge or the sending unit. I think the voltage stabilizer is ok as the fuel gauge seems pretty accurate.

Appreciate any suggestions or ideas.
 
Have you checked your thermostat.... maybe it's stuck open?
 
The thermosthat is new but that doesn't mean it isn't stuck. That still wouldn't account for the gauge only going half way when the sending unit is in boiling water.
 
On my GT6's six cylinder, when the temp gauge only moved about a quarter of its sweep, installing a new sending unit returned it to reading correctly. Pretty certain I've heard others having the same symptoms cured with a new sender.
 
Thank you, thank you very much.... for that info don
 
There is some minor misinformation on the page linked above. The "voltage reducer" is typically referred to as a voltage stabilizer. This is a minor point of semantics but when you are Googling for the part or searching for it in a catalog it will be listed as a voltage stabilizer. It does not supply 6-8V to the fuel and temperature gauges. It switches on and off rapidly (0V to about 14V... depending on the charging system output) to supply an AVERAGE of 10V. Because it is switching on and off rapidly, measurements taken with a voltmeter (particularly digital meters) will show something other than 10V. The meters are simply not designed to display an average value over several seconds.

Both fuel and temp gauges can be tested by shorting their sending unit wires to ground with the ignition on. Grounding the fuel gauge sending unit (green/black) wire should make the fuel gauge needle climb over the full mark within about 30 seconds. Likewise, grounding the temperature sender's green/blue wire should make the temperature gauge read above "hot" in about the same time.

Gauges designed to operate with the voltage stabilizer work by internal resistance heating. The sending units throttle the flow of current through the gauges and on to ground. Shorting the sending unit wires to ground allows the maximum current to flow and thus the maximum internal heating of the gauge which produces the maximum needle deflection.

Back to the original question from Airlifter, I would double-check the resistance measurements to make sure you were on the correct scale in both instances. The values seem quite high and if you really are seeing an increase in resistance when you heat the temperature sender, I believe the sender is faulty. I don't know the correct resistance range/values for your car's sending unit. However, I do know that the sender resistance should drop in value as it heats.

For reference, see the link below to a thread on a Jensen-Healey forum. In the first post the OP lists the decreasing resistance range of the Smiths sending unit matching his gauge. I am not suggesting these are correct values for the TR6 but that the resistance should drop, not increase with temperature.

https://www.jensenhealey.com/forums/view_topic.php?id=14
 
Right. Not only does the resistance have to go down to make the gauge read higher, but it has to be low enough to produce some heat in the gauge. (The gauge movement works on heat.) 260K is way off the mark.
 
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