My clock and fuel gage no longer work. Where specifically is the ground for the cluster? Thanks, Mike
Not sure where the ground is but most clocks don't work or stop working quite often unless they have been converted to quartz. The fuel gauge is another issue that happens often so it may not be a bad ground on the instrument cluster. I would find a good ground and run a wire to the back of the clock case (just touch it) to see if it starts working. That will at least tell you if the clock is bad or if the issue is with the instrument cluster. If the ground was bad on the instrument cluster I don't think any of the lights would work either. It may be grounded through the circuit board and one/few of the mounting screws. The fuel gauge tank sensor may be bad or stuck, not sure how to test that.
I have a ground issue with my low mileage 69 GS400, when I turn the lights on the gas gauge goes to empty. Have not looked into it, but see what looks like a ground wire that is hanging. As I remember there is a ground prong on a metal washer on the light switch, and this wise may go there. Need to investigate it but need to change the AM for a AM/FM and maybe a new speaker to get the radio working, so will look into the ground at that time. First time the gas gauge did not work, it was funny, I went to a evening car show and when I arrived I had 1/4 tank of gas, when I left, it was about dark the lights were on and the gauge was on E. Shut the lights off and had 1/4 tank of gas, and made it home OK.
Did you find your answer? If not, I'll take a picture later today. My gauge cluster is sitting in a pile and easily accessable.
Mike, Need some more information to diagnose the issues. First has your clock been modified? quartz conversion? The factory clock runs on a set of points that energize an electromagnet to wind the clock. This system is prone to failure. Second what does your fuel gauge read? Full or empty? You will need to find the tan wire in the trunk. Located near the trunk latch. this is the wire from the gauge to the sending unit in the tank. Unplug the connector. Your fuel gauge should read above full. Next connect the wire from the gauge to ground, your gauge should now read empty. The fuel tank sending unit has a range from 0 to 90 ohms resistance. The next test would be to connect an ohm meter to the wire that goes to the sending unit. What is your reading? Now add some gasoline to the tank the resistance should increase. More than likely your sending unit is bad and will need to be replaced. Third if you have a missing the ground to the dash weird things will happen. Had this happen to a car and when I turned on the turn signals the wipers pulsed with the lights.
This is where a set of test leads come in handy. A test lead is just a piece of wire with alligator clips on each end. A test lead will allow you to run a temporary ground quickly as a diagnostic tool. There's a great thread on here about how to diagnose a fuel gauge.
Guys, Thanks for all the feedback. I think the Clock needs repair as it won't pass the bench test. The fuel gage problem was most likely a bent back trace at the instrument cluster plug receptacle. I'm currently trying to get the Wipers to work. Many hours in so far. Jumper tests fine installed. Cleaned a lot of connections and taken a lot of VOM readings. I now believe the problem could be the connections on the rear of the control switch. The electrical connector are 90* rotated PIN TYPE set up for a 0.110" stud. Are these available, what are my options? I'm looking at all individual if I cant find replacement connections to fit within the holder for the back of the switch. Thanks All!
