Alternator charging system

LHERKO

MEMBER
1998 CHEVROLET ASTRO
6 CYL
2WD
AUTOMATIC
142,000 MILES

My van would not start yesterday, after running two days earlier. The battery seemed low. I took the battery out, ant it tested OK. I took the alternator out, and it tested as a bad diode. I installed a rebuilt alternator. But, the charging system is not working properly, I ran the battery down while driving today. What should I look at next?

4 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Did you check gauges fuse no.4 10amp and also have the battery load tested to check its condition-if it fails the load test replace it

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Load test the rebuilt alternator-an alternator if its good should be putting out between 13.5 to 15.5 volts with a high load being use such as heater/lights/AC

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Wednesday, October 1st, 2008 AT 5:11 PM

LHERKO

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8 POSTS

Rasmataz, thanks for your continued replies! I do not measure any dymanic voltage from the alternator at the battery, only the static 12v or less, regardless if the van is running or not. I have good ground between the battery and the alternator. The wiring diagram you posted shows a fusible link between the battery and the alternator. Could this be the culprit? If so, how difficult is it to locate on my van?

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Thursday, October 2nd, 2008 AT 10:46 AM

RASMATAZ

MECHANIC
75,992 POSTS

If you measure the reading there at the alternator battery terminal it should read the battery voltage -if not the fuse link is open

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Thursday, October 2nd, 2008 AT 10:49 AM

LHERKO

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8 POSTS

Rasmataz, continuity and voltage to the battery side of the alternator kept reading OK. So I pulled the new alternator out and had it tested, it was OK. So I looked at the wiring a little closer. The small wire, on the alternator, that goes to the gauge on the dash felt suspicious at the alternator connector. I spliced it back together, reinstalled the alternator, and everything seems to be working OK!

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Friday, October 3rd, 2008 AT 7:02 PM