rich weyand
Full Access Member
- Joined
- May 28, 2014
- Posts
- 967
- Reaction score
- 177
- Location
- Bloomington Indiana
- First Name
- Rich
- Truck Year
- 1978
- Truck Model
- K10
- Engine Size
- 350
One thing nobody here mentioned - and apparently wasn't the problem in this case - but whenever you have lighting or gauge issues, you should first check that the cab ground is in place. A lot of people replace an engine and don't put the cab ground wire in.
To review, there are four grounds on our trucks, and they all have to agree on what zero volts is: the battery, the alternator and block, the frame, and the cab. Four things, so three connections. The battery cable should have two wires on it, a heavy one and a light one. The heavy one goes to the block, and the alternator, which is electrically connected to the block by being bolted to it. The light one goes to the frame on the radiator cross-member.
The cab also has to be grounded, however. It's on plastic or rubber (insulating) shock mounts. The cab is grounded to the engine with a copper stranded cable from the firewall to the engine passenger-side manifold cover screw.
If that cab ground cable is missing, everything in the cab will be haywire, from the lights to the gauges. Things like: as the flasher flashes, the fuel gauge goes down to half, then back up, repeatedly.
To review, there are four grounds on our trucks, and they all have to agree on what zero volts is: the battery, the alternator and block, the frame, and the cab. Four things, so three connections. The battery cable should have two wires on it, a heavy one and a light one. The heavy one goes to the block, and the alternator, which is electrically connected to the block by being bolted to it. The light one goes to the frame on the radiator cross-member.
The cab also has to be grounded, however. It's on plastic or rubber (insulating) shock mounts. The cab is grounded to the engine with a copper stranded cable from the firewall to the engine passenger-side manifold cover screw.
If that cab ground cable is missing, everything in the cab will be haywire, from the lights to the gauges. Things like: as the flasher flashes, the fuel gauge goes down to half, then back up, repeatedly.
