What's Up, Doc? - Tech

The wire from the tach to the negative side of the coil was pulled through the firewall close to the coil.

Everything in the dash needs to be grounded-each gauge and each light. Some people simply ground everything to the mounting posts on the gauges and figure the panel will ground to the dashboard, and that may work, but I wasn't gonna find out. Electrical stuff is kinda like hieroglyphics to me. I have to think really long and hard about it all, and it made sense to me to run ground wires to the sheetmetal behind the dash, one for the gauges themselves and one for the lights for good measure. Like the ignition power wires, the grounds were hooked up the same way.

Here's where the real fun began-deciphering the stock harness! I got a wiring diagram for the stock harness-try Brothers Truck Parts-and that was all fine and dandy, but now I had to figure out how to read the schematics! After a few hours with my thinking cap and a test light, I got a clue as to what's what. Left to right on one side of the connector are the instrument panel lights (two gray wires), right turn signal (dark blue), left turn signal (lt. blue), high beam (lt. green), voltage dummy light (brown), and ignition power (pink).

The other side goes from left to right: ground (black), temp dummy light (two dark green wires), fuel sending unit (tan), empty terminal, parking brake dummy light (two tan wires), and oil pressure sending unit (dark blue).

All the wires will get cut in the end and the plug totally severed, but I'd recommend doing one wire at a time if you're as prone to Murphy's Law as I am.

Here's how the side with the empty terminal wound up: male to female connectors on the oil and fuel sending unit wires and butt connectors to cap off the dummy light wires that won't be used. I was unsure at this point about where I was going to hook up the ground wire, but I eventually capped it too in favor of going directly from the dash to a bolt through the sheetmetal under the dash.

All the wires on the other side of the plug went to their respective locations at the new gauges, and since that aftermarket temp gauge already had a wire going to the sending unit, I used it. It might look a little out of hand, but actually everything is hooked up at this point and ready to go. I routed all the wires from the gauges to the right side of the dash. They all went in at a common spot so there weren't wires going all over the place. Notice all the male to female connectors just inside the dash opening on the right; they are clustered together for easy access in the future.

Double-checking to make sure there were no loose wires or connections, I checked to make sure at least the lights would work before I buttoned everything up, and they did! The rest of the gauges powered up too, aside from the speedo, which is still cable driven. Sweet! The wires from the plug for the turn signal and high beam indicators were connected to the power wires on their LED lights, while their grounds were run with the rest of the gauges.

With the steering column loosened up, I put a rag over it to protect its new paint. I put the new gauge panel in place while being careful that no wires got caught up anywhere in the process.