Post 3 Fuel Gauge
When I put the wedge to bed everything worked, the car had just passed its MOT! When I un-wrapped the car in the spring, apart from the previous issues I described in post 1 the temperature gauge had stopped working.
Having checked this out it looked like the sender unit was not working - even though I had replaced it last year! I bought another one and fitted it and the gauge didn't work, frustrating, as it worked if you short the sender wire out, the normal test!
Resort then to the TR7 manual and in there is a nice explanation of how the gauge works. Judging from the diagram it looked like one of the fixed resistors may have changed value. Unlikely to have changed value but clearly one of the resistors must have shorted or similar.
My thought was could I change the variable resistor value by adding resistance in the circuit, so I have made an additional resistor, value 750 Ohms, and connected between the harness and sender. My first attempt, 1k Ohms put the needle too low and my second attempt, 500 Ohms put it too high! 750 Ohms however is just spot on, the needle sits at the half way point - not how it was originally!
Tested the gauge on a run to Warwick and back and all appears to be well - will monitor it over coming weeks
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| Extract from the TR7 manual |
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