1985 C20 Cluster Problems

[BowTies&Bugs]

I have been a long time reader but this is my first time posting.

I recently acquired a 1985 C20 LWB truck after wanting one for a long time. My hopes are to clean it up enough to make it my daily driver. I got the truck running and driving but have gotten hung up on some electrical issues. I have tried everything I know to no avail. I was hoping someone would be able to give me some advise.

Except for the turn signal indicators, none of the lights in the cluster work. All of the bulbs look fine. I pulled the cluster to see if the problem was obvious. The main connector seemed to be seated fine but there was a stray wire that was not connected to anything. I took a picture and attached it below. Could this be the ground? If so, where does it connect?

Also, this is probably not an electrical issue but the speedometer is not working. After I pulled the cluster out, I drove the truck to see if the inner shaft of the cable turned. It seemed like it did not turn even when I was going fast. Is it common for speedo cables to go bad? Or, is my problem lurking in the transmission?

Thank you in advance for the response! I look forward to getting this truck back on the road.

-Drew

[chrismoore701]

Check the bulb sockets on the battery. I had the pull the tabs out a little and put some dielectric. Grease on them and they worked. As for the speedo cable. Check the cable at the Trans be sure it is in. It is possible that I bound up and snapped. There is a small gear inside the Trans that spins the cable that also be stripped. Just some thoughts

Chriz

[ray_mcavoy]

Welcome!

Originally Posted by BowTies&Bugs

Except for the turn signal indicators, none of the lights in the cluster work. All of the bulbs look fine. I pulled the cluster to see if the problem was obvious. The main connector seemed to be seated fine but there was a stray wire that was not connected to anything. I took a picture and attached it below. Could this be the ground? If so, where does it connect?

That stray "wire" in your pic is a fiber optic cable that was used to illuminate the ash tray.

If you still have the cluster unplugged, use a test light or voltmeter to see if the gray wire on pin #2 of the cluster connector has power with the lights on. The cluster grounds are black wires on pins #3, #8, and #10.

If you don't have power on the gray wire, check the "INST LPS" fuse. Also rotating the headlight switch knob varies the brightness of the dash lights ... so make sure it didn't get turned all the way down. And sometimes the dimmer rheostat gets a little dirty/oxidized and prevents the lights from working (rotating the knob back & forth a few times will often restore power to the lights if that's the case).

But if you do have power on the gray wire, check the bulbs & sockets like chrismoore701 said. It's not uncommon for there to be a bad connections where the bulbs make contact with the sockets and where the tabs on the sockets make contact with the printed circuit.