Fuel Guage

[TR674]

Hello all and a happy new year.
My fuel guage as stopped working on a few occasions in the recent past. Going over a bump or taking a sharp corner usually restored operations. Now it is not working at all. Has the unit failed or are there numerous connections and/or earths secretly hidden that I need to check?
Regards
Craig

 

[DrEntropy]

System is grounded at the tank sender: a potentiometer-like device. Check those connections (and may as well clean 'em while you're there) first. The gauge connections (two) as well. Voltage is supplied from a voltage stabiliser at 10V to the gauge thru the green/lt.green wire, then to the sender with the green/black one. If you ground the sender G/B wire the gauge ~should~ climb to "FULL". If not, it may be time to pull the gauge and repair/replace it. This also gives you an indication as to whether it's the gauge or the sender causing the problem.

As yours is a "later" car the gauge is likely one using induction coils to move the needle. It probably has one of the hair-thin wires vibrated to failure. Before condemning the instrument, check thru the above, and ohm out the wire to the rear as well. Rule out all the "dumb stuff" so-to-say.

 

[dklawson]

DR, in your second paragraph are you talking about the "fast response" gauges? Those gauges use internal magnetic coils but they fell out of use during the mid-1960s when the stabilizer was introduced. To the best of my knowledge Smiths used the common bimetallic gauges from that point up until Austin/Rover started buying Nippon Seiki gauges.

The DR's test method is how to start. If with the ignition turned on grounding the green/black wire gives you a FULL gauge reading, focus your attention on the sender. If the test does not cause the gauge to read FULL, you must first confirm the continuity of the green/black wire between the tank and gauge. Once you know that the wire is OK you should look for problems with the sender.

 

[DrEntropy]

You're right, Doug! Ack! Apples/oranges... exactly backwards. Apologies.

...I'll blame it on "oldtimer's disease." /bcforum/images/%%GRAEMLIN_URL%%/blush.gif /bcforum/images/%%GRAEMLIN_URL%%/crazy.gif