Hoovw

On the way home from school, check gauges light comes on and notice the voltage gauge is down. Get home in about 20 minutes. 4-5 hours later I go out and start it up fine, but the gauge is now at about 11ish and in a few minutes drops back down again. Drive around for about 15 minutes just fine, come home turn it off and then turn the key to the run position and it is around 13. So I can't decide if the alternator is out and I am just running on battery or if the gauge is just not working properly. Any help is appreciated.

No DMM to test right now. Battery is 09. Alternator looks original.

Fsher21

Sounds like the alt. Not sure what DMM means, but when you are able to drive to an auto parts store, most all of the larger ones will test your battery, alt. and starter for free, as well as pull any codes you may have stored. If you cant drive it to the store, remove the alternator and take that in to be tested before you invest in a new one.

Hoovw

Digital multimeter, sorry. Will they test it with the scanner? I've only had them test alternators off the vehicle.

Fsher21

Not sure how they test it, sorry. Never pay attention when I have them do it. It takes like 2 minutes and they connect right to the battery, not sure if they have to connect to anything else.

1991Jeep_Man

Autozone has a load tester that hooks up to the battery. With the vehicle off, they test the battery volts and determine a good or bad battery. Then they ask the vehicle be turned on and held at 2000 rpm for like 10 seconds for an alternator output reading. That determines what's going bad. Also check all ground connections and the battery terminals for corrosion that would prohibit current.

tjwalker

1. Clean battery terminals and battery posts until SHINY. Also freshen engine grounds.

2. Verify low voltage with a meter (when you get one)

3. Bench test your alternator; this is likely the culprit.