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Changed Alternator charging light stays on


dr_jones2u
11-28-2007, 12:02 PM
The alternator died on my 1999 Trooper while on the highway. Had to jump it off several times to get it home. Had the alternator checked and it was bad. I changed it with no problems. Since changing it the charging system light stays on constantly and my Blower and AC don't work. (They were working before and I never got a charging system light before changing the alternator). I had the alternator checked and its putting out 14.5 volts and the battery is fully charged. I don't find any blown fuses. It starts and runs fine now. Any ideas?

boritz
11-28-2007, 05:21 PM
Possibly:

1. Check the ignition connector/wiring into the back of the alternator.

2. Bad regulator inside the alternator (I had this problem).

The alternator can still charge the battery even when there is a fault in one of the above.

dr_jones2u
11-28-2007, 05:52 PM
Thanks for the quick response! I double-checked the connections and they are good. Can the regulator be checked without pulling the alternator again? Will the test that the auto parts store does pick up a bad regulator? I figure they are going to argue with me about this! Thanks again

boritz
11-28-2007, 06:27 PM
I had to get an auto-electrician to check mine. I doubt if a parts store could do it.

Here is the thread on my trials and tribulations with the alternator:

http://forum.planetisuzoo.com/viewtopic.php?t=13757

The symptoms were not exactly the same as yours, but there isn't much else to go wrong with the alternator circuit if it is charging OK.

inafogg
11-28-2007, 06:31 PM
hi guys yea 1st thing in my head bad alt.!!!take it back

trooperbc
11-29-2007, 03:33 AM
you will find many a post about not buying an alternator for your isuzu from a bigboxpartsstore. their cheapy rebuilds can be bad out of the box.

buy from the dealer, or for good value and excellent results, a remanufactured by bosch unit.

//bc

dr_jones2u
11-29-2007, 10:59 AM
Thanks for the input guys. Looks like Im gonna pull it and take it back and screech at them until they give me another alternator. Thanks for all the help

copter steve
11-30-2007, 09:25 PM
Charging systems are fun aren't they? Ask the parts store if they can give you your original alternator back. Then go out and find a electrical rebuilder in your area to check out your alternator. The nippendenso alternator that Isuzu uses is a bullet proof unit. Usually they quit charging when the brushes no longer make contact on the slip rings. I agree with the opinion that you never know what you are going to get at a parts house. Never buy from the dealer, unless you have money to burn. Check your cables, always a overlooked area. I have seen cables that look good, but have corrosion inside the insulation.

Good luck

Copter Steve

dr_jones2u
12-07-2007, 05:49 PM
back to the drawing board. Took the alternator to my local alternator/generator rebuilder and he says the voltage regulator is fine..the unit is working fine. I just read about a charging relay. Anyone familiar with it and where it is on a 99 Trooper?

dr_jones2u
12-09-2007, 12:27 PM
new info, there doesnt appear to be any voltage to the blower and compressor fuses in the fuse box

atfdmike
12-10-2007, 09:18 AM
new info, there doesnt appear to be any voltage to the blower and compressor fuses in the fuse box

Your "new" alternator is bad. I have had the same problem when I replaced mine. The new one worked the first time I started it, next day, nothing. Take it back and get a new one and problem solved.
The HVAC not working is typical of no output from alt....engineers wanted to reduce drain on battery if alt not working.

dr_jones2u
12-10-2007, 05:17 PM
even though the battery is fully charged?

atfdmike
12-11-2007, 08:58 AM
even though the battery is fully charged?

Yes, the blower will not work if the alternator is not working, engine is running, fully charged battery.

dr_jones2u
12-15-2007, 03:09 PM
I finally got to the bottom of this. I got a parts guy at the local dealship who actually knew what he was doing to look up the alternator. It seems 99s built after August of 97, use a 90 Amp alternator..which he didn't stock and was 813.00 new. O'Reillys (and Autozone and Pep Boys) don't make a distincion so they sell the 75 amp alternators!! So O'Reillys can't get me a 90 amp neither can Auto Zone and my local rebuilder will have to find one. After several trips to the store O'Reillys refunded my money then I had to fight them over the core. I ended up keeping the 75 amp alternator since they couldnt come up with a core that I could have rebuilt. Anyway, I bought a used OEM alternator with a 3 year warranty for 90 bucks. I now have air and heat again and no alternator light. I know I'm on borrowed time with a used one but at least I have one that can be rebuilt next time. Thanks to everyone who helped. You were right from the first response I received.

gil581
12-22-2007, 05:45 PM
[quote=dr_jones2u]The alternator died on my 1999 Trooper while on the highway. Had to jump it off several times to get it home. Had the alternator checked and it was bad. I changed it with no problems. Since changing it the charging system light stays on constantly and my Blower and AC don't work. (They were working before and I never got a charging system light before changing the alternator). I had the alternator checked and its putting out 14.5 volts and the battery is fully charged. I don't find any blown fuses. It starts and runs fine now. Any ideas?[/quote.I HAD same trouble with my 98 jackaroo. After a couple of trips back to the auto elect, it was found to be the plug at the back of alt.Original has one power and 2earths, the replacement had one earth,but the plug looks the same They made an adapter (job done)

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