
Fuel Gauge On The Blink
#1
Posted 17 May 2014 - 09:52 AM
I've got a bit of a problem I've never seen before. My fuel gauge works whenever it wants to. So I tested it with a test light from the tank end. When I ground it the needle shoots to full so that's good.
But when I test it I get a blinking red light instead of a solid red light. Any idea what that could be ?
Ive never had nothing do that before. It probably explains why it works whenever it wants to...
Any ideas would be amazing !
Thanks all
Theo
#2
Posted 17 May 2014 - 11:13 AM
So I tested it with a test light from the tank end.
But when I test it I get a blinking red light instead of a solid red light. Any idea what that could be ?
If I understand your test method, you have disconnected the green/black wire at the sending unit and connected your test light between the wire terminal and earth. Is that correct?
If that is what you have done, the blinking light is perfectly normal. The gauge system from 1965 until the end uses a device called a voltage stabilizer to produce an average 10V to power the gauges. The stabilizer is an electromechanical voltage regulator. It literally switches its output between 0V and 12V to create the average of 10V. Each one is individually adjusted so it may switch once per second or several times per second. Each time the contacts switch your test lamp is going to blink. Your car's problem may still be with the stabilizer but the blinking light is normal.
When you say the fuel gauge works when it wants to, what exactly is it doing? If your car has an electric temperature gauge, what is it doing?
#3
Posted 17 May 2014 - 04:16 PM
Well for instants, I put £15 worth of fuel in it the other day. The following day the gauge said empty. Put another 15 yesterday and it shot up to were I think it should be.
Today it's at 0 again.
When I earth the wire at the sending unit the gauge goes up to full.
My temp gauge is the type that screws straight into the block (sorry not sure if that means if it's electric or not)
It seams to go upto 50% after some running so I assume that's working fine.
#4
Posted 17 May 2014 - 09:27 PM
Ok then. I have a suggestion for you. If you can pick up a sending unit gasket locally, buy one in advance of the following test.
Drive the car until you can shine a flashlight through the tank filler neck and see that the fuel level is BELOW where the sending unit enters the tank. When the fuel is below that level use a screwdriver and small hammer to tap the locking ring for the sender counterclockwise to unscrew it. Then remove the locking ring and sending unit but leave its wires attached. Turn the ignition switch to the run position and have a friend move the float arm on the sending unit from "full up" SLOWLY down towards empty as you watch the gauge. Have them do this several times and note if and when (position wise) where the gauge seems to drop to empty.
I anticipate that you will find that the float arm will repeatedly reach a certain point below which the gauge drops to empty . That behavior is consistent with a broken resistance wire inside the sending unit. Repair is by sending unit replacement.
Fit the new gasket and re-install the old sending unit. When you have bought the replacement sender, repeat the steps above to replace the sending unit. It would also be smart to test the new sending unit as described above just to make sure it works properly and fixes the problem.
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