I'm reinstalling everything back into the cab and am finally getting close to finishing up the dashboard. But now, as I said in the title, the instrument cluster is working backwards.

Signaling left makes the right turn signal come on and vice versa, and I'm pretty sure all the gauges are operating backwards (as in it shows I have 3/4 a tank of fuel instead of 1/4, etc.). The temp gauge also flicks with the turn signals for some reason.

Prior to reinstalling everything I just had the instrument cluster propped up on the steering column with the two plugs going into the back and it worked fine (and no other part of the dash installed). I'm pretty sure I tried the turn signals previously without the instrument cluster plugged in at all and they worked fine, too.

This seems like a grounding problem to me, but I have no idea what/where. What'd I do?

 

It sounds like a ground problem to me as well since you can only plug the instrument cluster in one way. There are supposed to be a couple of grounds behind the dash on the firewall, pull the screws out and grind the paint off around the screw holes and reinstall. If that does not do it check the continuity of the ground wires from the plug on and check for broken wires/corroded connections.

 

It sounds like you are having an intermittent Ground and the gauges are seeking their own Ground through another gauge and sender.

It could be as simple as wiggling the connector at the rear of the cluster.

Since you will probably have to take it out again you should repair the grounding problem forever like I describe in Part-3

As already mentioned unless you really try then it is impossible to connect it to the harness wrong.

Jim

https://www.dieseltruckresource.com/...d.php?t=209884

 

Soldering on that ground wire fixed it, thanks! Wish I knew where the problem came from in the first place though.