Speedometer and Tachometer not working properly?

1992 GMC SIERRA
300,489 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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RODJAMES
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My speedometer gauge bounces up and down periodically and most of the time reads max speed. I’m not sure if this is normal but my rpm gauge seems to be reading a lot higher than it should. How can I fix or diagnose this?
Mar 16, 2024 at 3:03 PM
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STRAILER
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Yep, this goes wrong when the cluster is going out or the system has a bad ground. I would remove the cluster and check the wiring connectors for corrosion. The ground is the black wire which a would test with the cluster disconnected.

This guide can help:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

If the ground is good, I would try a rebuilt/used cluster. Check out the images (below). Please let us know what happens.
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Mar 17, 2024 at 11:13 AM
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STRAILER
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Anything?
May 11, 2024 at 12:39 PM
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