1998 Acura SLX 6 cyl Four Wheel Drive Automatic 175000 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?
At 12.2 and 12.4 volts, the battery is not being charged by the alternator.
Did you test the voltage at the alternator main post when engine is running?
If voltage is between 13.5 to 14.5 volts, you have a bad connection between the alternator and the main fuse box or the main fuse is bad.
If it has similar voltage as the voltage between the battery terminals, the alternator is not charging and possible causes are : 1. Faulty alternator.
2. Alternator is not turning fast enough to provide adequate charge. Revv the engine and chack if the voltage increases.
Check the belt tension.
Check the harmonic balancer on the crank pulley if equipped. If the harmonic balancer is faulty, you would tend to see a wavy movement of the pulley and have belting noises.
The charging is not controlled by the PCM so there is nothing you need to do about it.
January, 20, 2010 AT 4:15 AM
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)
July, 14, 2010 AT 11:15 PM
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.
March, 11, 2015 AT 6:09 PM
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.