1998 GMC Jimmy battery or alternator problems?

1998 GMC JIMMY
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FUMINGRED
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1998 GMC Jimmy Four Wheel Drive Automatic

When I rolled up my window this morning it was very slow. I checked the gauges in the dash and they were all going down. I pulled over and turned off the engine to check under the hood. The belts and battery connections seemed okay. When I checked the gauges again they were all rising. After waiting for a few minutes, I turned the engine over again. All systems go. Then within 30 seconds all of the gauges started do go down again and the engine died. What is the deal? Battery or Alternator problems?
Apr 3, 2009 at 12:32 PM
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JDL
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Hello, I'd make sure the battery has a full charge, check that the cables/wires are clean and tight on both ends. Then I'd check the charging system.

If you use a digital multimeter, check the voltage reading across he battery posts, with everything turned off, around 12.6 is considered a full charge. Take a second reading, with the engine running, the second should be higher than the first, if it isn't, something wrong with the charging system. Wiring circuit or alternator itself.
Apr 3, 2009 at 12:58 PM