1985 CHevy in cab wiring harness....

[djohnsonpools]

Hello All,

I been ripping out my hair because my trucks cluster wasn't working. I found a local craigslist trucks that was being parted out and I actually got to verify and see all gauges worked before I removed it paid only $40!!

But to my dismay I brung it home pluged it in and just my luck the working cluster I saw working aint working in my truck. So I undid all the in cab wiring harness unwrap the electrical tape to check for damage/ corrosion etc. Only 1 wire needed to be resoldered.

Only one last area I notice could be where the problem is, the firewall connection plug the is greasy or so I'm cleaning the male ends with a razor knife and going to reassemble in the morning. AND try it again. ANy thoughts, or if you runned in to similar bull shniz I apprieciete feed back ..

-DJ

[mustardrocket]

I have the same problem with my cluster in a '78. I haven't gotten any farther than trying another cluster as you did. Please post if you find a solution. I will post also if/when I can get back to it.

[ray_mcavoy]

Have you checked the "GAUGES" fuse? I think some years are labeled "GAU / IDLE" because it also powers an idle stop solenoid on some engines. Should be over on the left side of the fuse box for 78-up with the plastic ATO/ATC type fuses.

If that fuse checks out okay, use a test light (or multimeter set to DC volts) to make sure you have power at the gauge cluster plug. For 78-up, the pink wires with black stripes on the cluster plug should all be +12V feeds with the key on. Also check the black ground wires on the cluster plug to make sure they still have a good ground connection. I believe they all lead back to a ground buss down under the dash by the parking brake so look for a bad connection there if the black wires don't have a good ground.

[gmachinz]

That firewall bulkhead connection doesn't have type of grease in it like you think it is, its a non-electrical waterproof sealant designed to resist moisture/water. You want to leave that goopy tar-like stuff in it.

[hatzie]

That goo is dielectric grease ^^. If you've cleaned it out get more and re-apply it.
The Packard 56 & Packard 59 connectors in the bulkhead plug are not sealed. Add water and you'll have a corroded mess without that grease.

Check the gauges fuse as noted above...
Still no joy?
I'd start then by pulling the cluster and turning on the ignition. Then test the Instrument cluster plug ground and power terminals one-at-a-time with a meter. All grounds to a good chassis ground with he meter set to measure resistance. Set to 20vdc scale, or another bigger than 12vdc and measure from chassis ground to each power terminal. The 1985 GM wiring diagrams can be found below in my signature.

73-87 instrument cluster connector pin-outs are here---> http://67-72chevytrucks.com/vboard/s...d.php?t=456878

[mustardrocket]

My gauges didn't work because the wire going to the back of the fuse in the engine compartment came loose. Reattached and everything in the cluster worked great