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Wedge TR8 temp gauge

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Airfix

Airfix

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Hi,
Iv'e just bought a 190 TR8, the temp gauge does not work.
The car came with a couple of old temp sensors and 2 other gauges. The PO has obviously tried the obvious fixes with no luck.
Any ideas? I plan on doing a continuity check of the wire from gauge to sender, apparently there is no voltage stabilizer in the Tr7/8. Is it possible that the circuit board in the instrument panel is u/s?
Appreciate any commetns or suggestions. /ubbthreads/images/graemlins/confused.gif
 
Knowing nothing about TR8s, I would start by removing the wire from the sender and touching it to ground. On most cars grounding this wire and turning on the ignition will send the needle to max hot... removing the wire from the ground will send it to max cold. If those tests work then the problem is probably the sending unit.

A test of the gauge should be similar but for that you'll need a wiring diagram or input form someone with specific advice on how the TR8 gauge reads.
 
I did some t/shooting last night, wire to the sender has 4.2 volts, there is no voltage stabilzer, just resitors on the back of the gauge to drop the voltage. Touching this wire to ground barely kicks the needle on the gauge. Checked the resistance on the sender appears to be normal at 1 ohm with engine cold.
Put 12 volts to a spare used gauge and grounded the output and the needle did go full hot. It's looking like the problem is in the gauge so time to pull the dash apart.
 
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