I have a '78 Long Bed, 5-speed, pretty much all original, build date 8/77. The CHARGE light stays on and the fuel gauge is pegged at E. Other than that, everything works normally. I remember having this problem years ago, but don't remember what eventually fixed it. I changed the alternator with a known good one (the one that was in there wasn't that old), checked the grounds, fuses, battery voltage and the connections at the fuel tank. Any ideas? Thanks in advance.
I'm not sure about your alternator, but my fuel gauge wasn't working when I bought mine. I checked it and of course it wasn't plugged in at the fuel tank. Then it would randomly go to full then empty while driving. Long story short, turns out it was a bad sender and cluster, probably rare in my case. I got both at a junk yard. It might be a pain to drop the tank, but it could be the sender. But if your alternator works and the light stays on, maybe the cluster? just my two cents
my truck, 79 shortbed, has just started doing the same thing... charge light stays on and my gas gauge is all wacky and never goes above a half tank even when its full. i thought someone siphoned my tank when i got in it yesterday but it was just the gauge acting up. any other thoughts regarding this??