Mark S M

Thanks for all your info. It does seem to be just dirty contacts in the gauge. When I first bench tested the gauge I only attached to the yellow red and yellow leads. I had the old sending unit to work with and when doing it this way I had steady readings. This morning I attached the ground as well and low and behold I had a mis-reading, bouncing gauge. I opened the meter and saw the contact points you mentioned and cleaned them with some fine emory cloth. I also made note of the adjustable contact position and turned it back and forth a couple times then returned it to its original position. It seems to be working properly now. Once I get the dash back together I will try it on the road and report back. The only question I have now is do I replace the 48 year old instrument lights that are still working or do I leave them as it seems they have proven themselves.

Thanks for the feedback and info. I measured the voltage at the meter and it was steady. I even jumpered right from the fuse box to the meter and there was no change. At this point I believe it is the meter as well. I will pull it and test on the bench again, that was why i was asking for the current levels so I could check the performance.

It is only the gas gauge that I am aware of. The needle moves up and down about 10-20 times per minute. I put a temporary ground from a chassis screw that I cleaned well and hooked it directly to the yellow lead at the sending unit. The gauge will run up to full but will then drop down to 3/4 and proceed to oscillate around that point about an 1/8 of a tank in either direction. I have also by passed the sender lead with an external wire from the sending unit to the fuel gauge connector and no change. Does any one know what the current through the gauge should be for full and empty readings?

Thanks for the responses but they don't explain what I am seeing. When I turn on the ignition the gas gauge will move up to half full then drop down to about an eighth and then start moving up and down between those two points.

I was wondering if this issue ever got resolved. I have been chasing the same thing on my wife's 72 Z. From my work it seems the feed to the instruments is unstable. The supply voltage at both sides of the fuse is good but the voltage at any of the three sending units, gas-water temp-oil pressures bounces from 1 to 6 volts. The feed to the meters is a yellow- red wire but some where it connects to a green feed line, does anyone know where the two wires connect or is it internal to the harness? Thanks