76 f100 ranger xlt 302 3 speed on column with gauges not idiot lights.
all gauges read low, fuel gauge read 3/4 when full and temp and oil pressure almost to the "n" in normal is as high as it goes. changed the cluster voltage regulator. Now they read even lower, fuel goes between 1/2 and 3/4 when full. If I ground the wire at the temp and oil pressure sendors on engine the gauge goes all the way up have not check the fuel like this yet. What could be the problem and what to check next. and fuel tank has a new sendor unit in it also.

 

It sounds like the oil pressure and temperature sending units may be bad. As for the fuel gauge, it could be a bad sending unit, stuck float, or poor ground out at the tank. You'll want to do the same ground test you did on the others first.

 

Dude, that would be a hell of a coincidence wouldn't it?
I hate answering questions with questions but is it possible the wrong circuit board was installed by you or a PO (you have gauges and one for lights was installed)? Make sure that your voltage regulator circuit board snaps didn't crack around the buttons when you swapped them out and if they did just solder them. There's also that little metal bar that might not be making good contact. I believe your problem is in the instrument panel somewhere...

 

Please re-read his original post:

This test proves out everything upstream of the sending unit, including the entire instrument cluster - coincidence or not. Each sending unit's job is to control the current through the gauge to ground, which in turn controls the needle deflection. Grounding the sending unit lead effectively shorts out the sending unit and maximizes the current through the heating element in the gauge. If this causes the needle to peg all the way to the right, then everything in the dash is functioning normally.