# Erratic Gauges

**URL:** <https://community.cartalk.com/t/erratic-gauges/30088>\
**Category:** Maintenance/Repairs\
**Created:** [May 5, 2009, 10:58pm UTC](https://community.cartalk.com/t/erratic-gauges/30088 "2009-05-05T22:58:42Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![benha1](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@benha1](https://community.cartalk.com/u/benha1)\
**Post date:** [May 5, 2009, 10:58pm UTC](https://community.cartalk.com/t/erratic-gauges/30088/1 "2009-05-05T22:58:42Z")

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So I just bought a very old-n-rusty 1989 Suburban to use to tow a boat back and forth to the ramp. It is, overall, a junker, but it’ll do what I need it to do. However, the gauges all read weird. The gas gauge oscillates around slowly. The voltage gauge does the same. And the oil pressure reads high for a while, and then drops to nothing, and then comes back. Any ideas on where to start with fixing this?

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**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\
**Post date:** [May 5, 2009, 11:06pm UTC](https://community.cartalk.com/t/erratic-gauges/30088/2 "2009-05-05T23:06:33Z")

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Start with a thorough check of the starting system. Don’t forget the battery cable connections too.

Your symptoms are symptomatic of an alternator with a fried diode in the bridge rectifier portion. But don’t let me troubleshoot it from here, check the system out from there.

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**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\
**Post date:** [May 5, 2009, 11:42pm UTC](https://community.cartalk.com/t/erratic-gauges/30088/3 "2009-05-05T23:42:42Z")

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Rusty? Start looking for bad grounds.

Tester