I have an 88 w100 with the 318. All my gauges, except the amp gauge read low. Coolant is only 2 marks off of cold, fuel reads little less than half when it should be almost full, oil gauge is low. I replaced the voltage stabilizer with a new one, twice. First one pegged the gauges. Second one reads lower than the original. My local salvage yard had 2 gen 1 trucks, and one was an 88. Pulled the fuel sending unit, pulled both voltage stabilizers. These stabilizers read same as my old one. Replaced fuel sending unit. Same results. I'm a bit at my a its end. Dan

 

if you think the voltage regulator is the issue this is likely the best way to try dealing with it.
https://www.allpar.com/threads/get-e...ost-1085245432

 

crazzywolfie, you are great. Thank you for sharing that link. I will try it and let the forum know.

 

to tell the truth i never found the stock gauges did much except for the gas gauge. the amp gauges never move much and the oil pressure gauge also never moved much even when doing 80. i also opted for a aftermarket temp gauge. if it is not too hard to do you could alway pull the fuel sending unit and test it. i forget the exact resistance reading but pretty sure full is almost no resistance and empty is about 70ohms. also if you hook it up to the wires and move it up and down while watching the gauge it should give you an idea if it is working.

 

Got it. I am not apposed to installing external gauges. I've had an external oil gauge for years. But I'm trying to restore the truck and trying to use original equipment where possible. thanks