1987 Mustang GT stock gauge cluster not working... Need Help

Smooth0087

New Member
Mar 11, 2011
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I am reassembling my stock 1987 Mustang GT and I'm having an issue with the gauges. The Tachometer, Oil, Temp, Fuel, and Battery gauges will not work. They do not even reset when you turn on the key. Does anyone have any ideas on what might be the issue? All the lights on the cluster work accept for the 4 indicator lights grouped on the bottom right of the cluster for fuel, low coolant, ect. My fuses are all good and I have swapped clusters and it still is getting no readings or power to the gauges. Any help will be greatly appreciated.
 
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I dunno for sure, but it certainly sounds like a bad voltage regulator on the back of the cluster. Though you did say you swapped clusters, the chances of having a bad regulator on both of them (providing the old one was salvage) is actually pretty high. The other thing I can suggest is that you make sure the ground circuits on the printed circuit board are intact and that there aren't any shorts or melted wires at your cluster's wiring harnesses. If you have a volt meter, check the respective wires for current.

This is a wiring diagram for your 87 cluster wire harnesses, it'll tell you what pin does what, and will help you greatly:

http://diagrams.hissind.com/?p=257
 
Looking at that diagram I'd definitely check the first harness, pin/wire #2. That's wire is the ground for that harness. The reason I say check that particular harness is that all the stuff you mentioned that has gone bad is on that one harness.