Ok,

History: 03 wagon, 84k miles, cobb stage II
Electrical mods: Headlight harness (directly from alt/bat wiring, but stock wattage GE nighthawk lights), direct power run to KSC-SW1 powered subwoofer, Alpine head unit, upgraded speakers.

I replaced my battery about 6 months ago after I realized that it wouldnt hold a charge, but the funny thing was that I would only have problems if I drove to work at tach speeds of 3200rpm or higher (usually for 25min). I thought that it could just be the battery and a slight possibility that the alt wasnt charging under load at that rpm or higher. New Advanced auto battery, and all problems seemed to dissapate. This was done at the END of winter and the outside temps were stabilizing ....meaning that after the replacement, I didnt have to use defrost/ac etc accessories very often.


I had a speedy run to work, keeping the tach at 3300rpm almost all the way to the job.

Yesterday night, I fired it up at about 2am on my way out of work, and due to some condensation I turned on the rear defrost, front defrost, headlights, and had the stereo on. I noticed immediately on a fan cycle that the lights got REALLY dim. I warmed up for a little over a minute.

Then on the way out of the parking lot, I noticed that the lights dimmed a couple more times. After about 15mins everything seemed ok. I made almost no stops, and noticed no dimming after a couple of stoplights near the end of my trip.

So I reasearched the alternator for this car on nasioc..... lots of searches, it bothered me all night.

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So today at about 12pm, I decided to check over my electricals. I cleaned and reattached the grounds on both fenders, and the grounds on the intake. I checked over the terminals, everything looks tight.

Battery reads 12.21v, seems OK.
Start car, battery reads 14.4, seems OK, charging. Still warming (2000rpm)
Lights on, 14.3v
A/C on, 14.1v
Defrost on 14.0-14.2v

I then notices that when the a/c compressor turns the fan on, it appears to have that typical piston slap noise louder. It goes away with a little throttle, but its more pronounced when the car is not warmed up. The noise also goes away when the a/c is turned off or I reduce the electrical load on the car.

It warms up.

With all the accessories on, its reading 12.21v at idle. IS THIS NORMAL? Shouldnt I be reading at leas SOME charge at idle with the accessories on? If I shut down anything electrical, it rises to about 14.1v at idle but 12s seem a little low for even at idle. I havent checked at rpm levels for changes....

As I engage the different accessories one by one, it drops the voltage like a rock. Is the regulator not doing its job? I thought it would drop and then rise to an acceptable level but it just stays at 12.2 and doesnt seem to rise.


Also, is it normal to have louder engine tapping when there is greater electrical strain. It doesnt seem to be present after the engine is warmed up.

Please help me before I give up and buy another alternator and waste 200 dollars ...or am I being paranoid

thanks
j

Anything above 12v is charging, I am not sure what you are getting at. Voltage is only one part of the equation, you should check the amperage as well. However at idle with accessories on I've seen cars anywhere from 12.3v to 13.1 with good alternators.

Hmm..

maybe it was a freak situation. I did come out to my car to find that the irrigation system for the building was watering the front of of the grill pretty good. Perhaps I got water in something that caused the issue.

If the alternator can charge the battery above 12v, then that should be ok, but I really thought at idle it should read above 13 even with the accessories on.

If the alternator can charge the battery above 12v, then that should be ok, but I really thought at idle it should read above 13 even with the accessories on.

Not always, I've seen plenty of times you can actually just barely break even with everything turned on at a slow idle. toss in a big stereo and you might end up discharging.

A new battery should read 12.45V to 12.66V with engine off to be fully charged. 12.24 is 50% !
only at 11.89V is a zero state of charge.

with engine on and no load an alternator will maintain a battery at 13.6V to 15.1V. With a load and @ 2000 rpms a quick dip and back to 13.6V to 15.1V.

Get your good battery to a full charge and replace the Alternator. Do not use a new alternator to charge your battery. Alternators only maintain charge and will possibly be damaged with a low battery.



Christian

Well I checked it today cold after sitting all night and the bat reads 12.51v. It may have been a freak incident or a sign of things to come. My load was being measured at ~500rpm warm idle so this may just be the behavior of what its supposed to read. I did clean up the contacts to the grounds, attached and greased with dielectric stuff.

I may do the grounding mod this weekend but didnt want to aggrevate the condition since I have an inspection on Friday and didnt want to go through the whole ecu reset just yet.

j