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1998 Acura SLX not charging

Tiny
LADAGO
  • MEMBER
  • 1998 ACURA SLX
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
Im only getting 12.4 volts at the battery. The battery is new, Im on my 4th alternator from napa in a month. The first one showed 14v at the battery for 2 weeks, everyone since has been 12.2-12.4 This last one I took off the car and had tested at 2 different places both tested it good. When this all started I was having weird idle problems, it would rev up to 2000 rpm at stop lights ect. I think my problem is with the ecu, can it be reflashed or reset somehow to let the alternator charge again? If not, where is it located, and how difficult is it to remove?

1998 Acura SLX/Isuzu trooper
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Tuesday, January 12th, 2010 AT 5:42 AM

5 Replies

Tiny
LADAGO
  • MEMBER
  • 4 POSTS
I ended up taking it into a shop, Ill try to explain it best I can. The alternator is controlled by the ecu, the circuit that tells the alternator to charge is not sposed to be grounded unless low alt output is needed, mine was grounded all the time. Telling the alt not to output anything(they tested it 12.4v@1amp). After finding the circuit, they clipped the wire that was causing the trouble and alt is now charging at 14.2@78amp.
Lesson learned: dont pull off battery cables while car is running to check if alt is working, it can fry your ecu and make your alternator not work, and make you think your going crazy. To fix it back to factory, I will need to get a new ecu and reattach wire. The wire is under the main battery connection(the big white wires next to the fuse box and battery) it is white with a blue stripe(I think that is the color I can double check tomorrow)
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Wednesday, January 20th, 2010 AT 4:15 AM
Tiny
SLOTHONE
  • MEMBER
  • 1 POST
You saved me! Thanks. Same story here. 98 Acura SLX. Alternator only putting out 12.5 volts. New alternator did not help.

I found and clipped the white wire with blue stripe as you mentioned. Seems to be working fine now, i'm getting 14V.
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Wednesday, July 14th, 2010 AT 11:15 PM
Tiny
VAUGHN HAMBY
  • MEMBER
  • 1 POST
Perfect fix! I'm going to trace the wire back to the fuse box though. I need to find the circuit that controls that ground. I'm sure we can do it without replacing the ECU. I hope anyways! I'm getting 14v at the battery. I checked and cleaned all grounds on the frame and block before I cut the wire. Nothing seemed to work, even a module by the valve cover I unplugged and it made no difference.
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Wednesday, March 11th, 2015 AT 6:09 PM
Tiny
JACKCAN
  • MEMBER
  • 1 POST
It would be nice to know which electrical box causes the issue. The one midway between the battery and main fuse block has such a wire.
However it's attached to a terminal so it may well light up all three wires
open testing it's a ground at all three wires.
Knowing the correct one because that might kill all three grounds would be useful.
JC
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Saturday, June 26th, 2021 AT 2:50 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Just to give more detail on this. The way it works is the PCM controls the alternator through what is called the field control. Basically the alternator is always spinning and generating current but there is a regulator inside the alternator that the PCM controls based on needed load.

This white and blue wire is this control wire. If you are cutting this wire then you are going to have the alternator put out 14 volts all the time and even higher in high RPM situations because the PCM is not controlling it. This is not a good thing. You need the PCM controlling this so that the alternator is producing the proper voltage for the demand. You can actually overcharge and explode your battery if the PCM doesn't have control over it.

This is most likely not a ground issue of one of the 3 grounds for the battery. This is caused due to the PCM not controlling this circuit as the PCM is most likely shorted internally and it cannot control it any longer.

More than likely the only fix for this is replacing the PCM assuming the alternator passes this test in this guide:

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

Below is the wiring diagram where you can see this circuit and can test the voltage on this circuit to see what the PCM is telling the alternator to do.

Let us know if there are more questions. Thanks
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Saturday, June 26th, 2021 AT 5:13 PM

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