[Unresolved] Gas and Temp Gauges not Working

[Ram50Guy01]

So, my gauges are being problematic. Spedometer works ofcourse. My gas and temperature gauge however do not. They will randomly work here and there but only for literally 2-3 seconds and tend to move back and forth in the process. I’m thinking it’s a bad ground but I don’t have any idea. I am currently at work so just wanting to see if I can get some information or tips before I get home and mess with it.

Also, it’d be pretty nifty if I could get information or diagrams on the wiring and the actual 7v converter location and whatnot

[FMS88]

Also, it’d be pretty nifty if I could get information or diagrams on the wiring and the actual 7v converter location and whatnot

Since you didn't mention a tach, I'm assuming you have the non-tach cluster. Here's the schematic for an '88. I'd be surprised if it differs for your '89.



You're right to suspect grounding issues since both gauges act similarly. The ground point for the cluster is behind it (see below). Inspect and clean the contacts of the two connectors that plug into the cluster if they're discolored or corroded. Also, clean the ground points of the negative battery cable in the engine bay. There are three or four points along the cable. Keeping those connections solid and clean can correct or prevent many electrical problems. If this doesn't do it, check fuse #7 and the connector to the ignition switch for poor contacts. If the problem still persists, get an Ohm meter and check the continuity of the relevant wire.
I don't know the location of the 7v converter. The diagram above shows a voltage limiter (*3) as part of the cluster. It's probably in the circuit board.

Here's the cluster ground location:

[Ram50Guy01]

I took the cluster out last night with what little time I had to mess with it. I checked continuity across the cluster which was fine. The only issue was I had no voltage coming in at the connection points for those two gauges and the 7v. I can’t really read the diagram you provided as it shows blurry on my end.