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Post by Father Ted on Jan 1, 2018 16:23:59 GMT
The fuel gauge on my Zephyr stopped working this morning (or somebody stole all my petrol at Brooklands).
The tank is almost full but the needle was wavering between empty and a quarter full.
When I got home I tested all the wiring and it seems OK. When I switch on the ignition the needle goes to about a quarter and then drops back to empty.
The temperature gauge and fuel gauge are both connected to the same terminal on the voltage stabiliser and the temp gauge is working OK, so does this mean that I can rule out the voltage stabiliser?
If so it must be the fuel gauge itself or the sender unit, both of which are unobtainable...
Any ideas on how to check which part is faulty? |
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Post by harvey on Jan 1, 2018 16:56:53 GMT
If you earth the wire on the tank sender unit with the ignition on, the guage should go to full, if it doesn't then the guage is at fault. If you have two wires on the sender (supply and earth) join them together to check the earth and the same thing should happen.
It could be that the float on the sender unit has developed a hole.
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Post by Father Ted on Jan 1, 2018 17:14:29 GMT
Thanks Harvey!
I have done as you said and the gauge went to full, so does that mean the sender is faulty?
If I put a test light between the feed to the sender and earth, it pulses on and off. Does that sound right?
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Post by harvey on Jan 1, 2018 18:50:39 GMT
Thanks Harvey! I have done as you said and the gauge went to full, so does that mean the sender is faulty? If I put a test light between the feed to the sender and earth, it pulses on and off. Does that sound right? Sounds like a sender problem then, so it could be the float holed. Best thing is to remove it and have a look. I've not done what you've done so don't know whether it should pulse or not. |
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Post by Father Ted on Jan 2, 2018 18:42:04 GMT
Sorted!
It was a bad earth, like so many old car electrical problems.
Previous owner had removed the sender unit and for some reason used lots if instant gasket to stick it back in place. This was preventing the sender from making a good earth contact.
Thanks for your help, Harvey.
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Post by chris1850 on Jan 11, 2018 0:13:58 GMT
FWIW the pulsing is normal. The voltage regulator output is a very slow variable mark-space ratio to maintain a long term constant average voltage. The gauges are even slower responding thermal types. If you look very closely at a gauge needle showing a "steady" reading, you'll see it quivering a bit with the on/off output from the regulator.
If you replace the regulator with a modern solid state unit, the output will be constant and the pulsing no more. A 7810 type linear regulator is the DiY choice.
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