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Old 01-11-2019, 02:44 PM   #1
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Charging System Light - '97 Jimmy

My '97 Jimmy (~180,000 miles) is showing the charging system light when the key is turned to the "on" position but not while the engine is running. The voltmeter on the dash reads 9-10 V at this time as well.

Once the engine is started (starts without difficulty) the dash voltmeter reads 14 V and I don't have any performance issues. (I have some other electrical gremlins but they are not recent developments and have not changed since this issue began.)

A few weeks ago we were out of town for about 10 days and I came back to a dead battery. I replaced the battery, drove to my in laws for the holidays and couldn't start the engine after stopping for gas. I got a jump, continued on my way and later replaced the alternator and battery cables.

The charging system light is still on when the key is turned to "on." It does not turn off after a few seconds like the other gauge lights.

I have pulled the new battery, new alternator and even the starter motor and had them checked at the parts store. All check out ok.

Should I worry about this? If so, where do I go next?

Thanks for your help.
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Old 01-12-2019, 01:46 AM   #2
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Re: Charging System Light - '97 Jimmy

What you are experiencing is known as a "bulb test" to be sure warning light bulbs are not burned out. perfectly normal....I would be worried if I did not see the light come on....
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Tech II (01-19-2019)
Old 01-19-2019, 10:34 AM   #3
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Re: Charging System Light - '97 Jimmy

Like brcidd said, the bulb is working correctly....this is a bulb check with the key just on, and it should go out when started if the alternator is charging....

You have changed just about everything, cables, bat, and alternator......

You should double check the charging system, when the engine is WARM....

Check bat cold.....with key out of ignition and nothing on, fully charged bat should be 12.6 volts with voltmeter across battery....

Start vehicle, and should read over 14.0 volts.....also does voltmeter read same as gauge?.........

let vehicle get to normal op temp...turn rear defog on, lights on, and blower on hi.....this "loads" the system.....reading may dip below 12.0 volts......rev engine to 2000 rpms.....reading should go above 13.0 volts....if you get these readings, charging system should be ok.....

If vehicle is not started for several days or more and then needs a jump, I would suspect a parasitic draw....
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