Triumph Repair: help, voltage stabilizer, stock setup

Question
hi my mate just got a triumph sorry not sure what year or make but hes having some problems with the electrics.. the wire that goes to the temp sensor is just suppose to measure the resistance of the temp sensor right will there is pulsating 4 - 9v on it whats the propblem he does want to turn it over incase it starts a fire can u please help


Answer
All a temp sensor is, is a resistor that changes its value depending on temperature.  On the other side of the gauge, there is a voltage stabilizer that provide +10 volts to the gauge, and the temp sensor provides the path to ground.  Depending on the resistance at the sensor, the gauge reads accordingly.

There isn't a reason the voltage would pulsate on a stock setup.  You might have an intermittent ground.  The typical failure in a temp sensor is it shorts out, and the meter will read higher or peg the needle at H.

I don't have the specs, but a temp sensor should be only a few hundred ohms, and steady at a fixed temp.  If you have pulsing or intermitted readings, check the path of the wires to make sure
1) voltage stabilizer is sending +10 v
2) wire leading to temp sensor is not grounding out

A new sensor and wire will likely resolve the issue.

Take a look at the triumphspitfire.com website; they have some technical information that may help, like the link below

http://www.triumphspitfire.com/gauges.html

I doubt a faulty temp sensor will start a fire; you have to be more careful about gas leaking onto the exhaust manifold when it comes to spitfire "fires"