Temp gauge more like a rev counter???
Discussion
Having put the car back together all is well again, taxed and MoT'd and ready to go. EXCEPT the fuel gauge is acting like a rev counter in reverse, i.e. it is showing temp but when the car revs the needle drops corresponding to the revs.
Has been suggested that it's an earth fault, but nothing obvious. Another suggestion is this thing...
which I think is some kind of ballast resistor, but my memory is failing me.
Come on clever chums, electrics is not my strong point so am i on the right track, how can i test for the fault, and if i need tio replace said item, what is it? Picture is sideways on btw, and the said part is attached to the bulkhead. (this is old skool S1 stuff).
Has been suggested that it's an earth fault, but nothing obvious. Another suggestion is this thing...
which I think is some kind of ballast resistor, but my memory is failing me.
Come on clever chums, electrics is not my strong point so am i on the right track, how can i test for the fault, and if i need tio replace said item, what is it? Picture is sideways on btw, and the said part is attached to the bulkhead. (this is old skool S1 stuff).
I think your picture is of a resistor used to dim the instrument lights.
Many older cars used a voltage stabilizer to overcome fluctuating battery voltage causing erratic instrument readings.
Never found one on my car and there isn't one shown on the wiring diagram for S's.
Basic circuit is live to gauge then from gauge to temperature sensor on engine which goes to earth. Hotter the engine the less resistance, more voltage passes so gauge rises.
Disconnect cable from sensor and gauge should read cold, touch it to good earth and gauge should rise to hot.
If it does this gauge appears ok, suspect sensor. If it doesn't I'd suspect a bad connection somewhere before doubting the gauge itself.
Are all other gauges (oil pressure, fuel and volts) reading about right ?
phillpot said:
Are all other gauges (oil pressure, fuel and volts) reading about right ?
Slightly difficult to say, as one of the jobs i had done was to change the fuel tank and sender! It's possible that the oil gauge is reading slightly lower, but none are doing the 'rev counter' thing. I'll check the wiring like you have said and see what's what. If not that then looks like a new sender.
Donnysoutherner said:
Having put the car back together all is well again, taxed and MoT'd and ready to go. EXCEPT the fuel gauge is acting like a rev counter in reverse, i.e. it is showing temp but when the car revs the needle drops corresponding to the revs.
Dodgy earth sounds like a possibility but if not that I'd wonder whether it's wired up wrong. Could you clarify which gauge you're talking about - fuel or temp? Is the effect exactly proportional to revs, or just that the reading varies with acceleration or road speed?The temperature gauge is VERY voltage sensitive. A few 100mV will make a noticeable deflection of the needle. If the voltage goes up on the gauge supply, the reading will drop.
So as the alternator spins faster the charge increases and the terminal voltage rises.
Check battery condition, earth straps, alternator.
So as the alternator spins faster the charge increases and the terminal voltage rises.
Check battery condition, earth straps, alternator.
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