77 K20
Full Access Member
- Joined
- Nov 9, 2012
- Posts
- 3,118
- Reaction score
- 3,188
- Location
- Montana
- First Name
- Mike
- Truck Year
- 1977
- Truck Model
- K20 5" lift
- Engine Size
- HT383 fuel injected
My dad and I did a 6 hour road trip in his 1979 GMC K15 yesterday and I got to drive his truck. I had only made it about 50 yards from his house and was checking out his gauges and saw the volt gauge was only reading about 12 volts. Stopped and turned around and went back to the house. Had him dig out his volt meter.
He swapped out his alternator he said probably 8 years ago for a 1 wire alternator (instead of the factory 2 wire). But said the volt gauge was working. I verified at the battery it was getting 14.0 volts. Went on the trip. On the 3 hour drive there it would hop up to 13.4 volts or so for a few seconds, then drop back to 12 volts where it spent most of the time. On the drive back it was about 50/50 whether it was reading 13+ or just 12 volts.
Any ideas? Where does the factory volt gauge tie into the trucks electrical system? Fuse box? Wanted to measure the voltage there... or is the gauge itself going out? But why drop to 12 volts? Figured if the gauge was going out maybe it would read 0 volts...
He swapped out his alternator he said probably 8 years ago for a 1 wire alternator (instead of the factory 2 wire). But said the volt gauge was working. I verified at the battery it was getting 14.0 volts. Went on the trip. On the 3 hour drive there it would hop up to 13.4 volts or so for a few seconds, then drop back to 12 volts where it spent most of the time. On the drive back it was about 50/50 whether it was reading 13+ or just 12 volts.
Any ideas? Where does the factory volt gauge tie into the trucks electrical system? Fuse box? Wanted to measure the voltage there... or is the gauge itself going out? But why drop to 12 volts? Figured if the gauge was going out maybe it would read 0 volts...
