Voltage issues...again

[One Equals Two]

Sorry guys in advance. I feel like I am beating a dead horse here.

First off, I know normal voltage is 14 ish, (12.5 ish with the battery only) etc. etc. I've had two local DSM guys try to help me for the past 2 months and none of us can figure out what the hell is going on now.

So, a run down. I have a 98' GST, 880's, slim fans running on all the time, DSM link, 800 W alpine system with battery in back, electronic boost gauge, oil pressure gauge, (a few but not too many electronic gizmos). The orignal alternator died (NO POWER STEERING LEAKS, OR ANY OF THE NORMAL ALTERNATOR KILLERS. Trust me, I've been there way too many times).

So, I replaced it with a Duralast one. Afterwards, 12.8 volts running with no fluctuation in voltage with rpms. After 5 or 6 minutes, the voltage steadily dropped to 12.2 and stayed there.

I thought it was just a bad Autozone alt (I've had that happen before). So I had it tested (but the test said everything checked out), but got a new one anyway. The new one tested okay too.

I put it in the car and no improvement with the exact same symptoms.

I suspected a short, but after voltage drop testing the car twice, I found none.

Also, I left the car for 3 weeks in the garage and when I came back, the battery was alive and well and it fired right up.

Anyway, I redid all the grounds, replaced the alternator choke, reground all the contact points, and made sure everything was perfect. Then, still no improvement.

Then my buddy with a TSi suggested that I needed more amperage because it was obvious the voltage regulator wasn't functioning or overheating or something because the volts never changed with rpms.

So, I dropped a few hundred bucks on an OEM Galant alternator 90 amp, and the voltage went up by about .2 volts, but the same thing happened. It gradually went back down and stayed down. So, this time it registered 13.0 volts instead of 12.6 or 7 (no fluctuation with rpms) and then 5 or 6 minutes later, dropped back down to 12.2 and stayed there. The alternator was hot.

I thought that it was just not sufficient to power the stuff on the car, but it seems like some guys use the stock alternator with more electrical load than I have.

Anyway, I suspected the ECM or something was bad, but it checked out just fine. Also.

I am just wondering, could it be that stupid little alternator connector? I heard these tend to give these cars random problems despite if they look good. I am fresh out of ideas and have done everything I am my DSM buddies could possibly imagine. If it's that connector, I'll be happy and mad at the same time. THanks guys!

 

[moi1463]

If you have a voltmeter, check the voltage coming from the alternator then check the alt fuse.

 

[One Equals Two]

12.45 volts at the alternator, already replaced the alternator fuse.

I guess I should mention that the main reason this is a problem is because the car isn't able to rev past 3500 rpm. Fuel pump is probably starving cause of the low voltage (kind of a duh).

Strange question to add, Is it possible that my car (w/DSMlink) was "tuned" for a certain voltage regulator setting? Like, tuned for a certain alternator, and I messed it up when I put this one in? I am wondering because the day after I had the car tuned, it started doing this low voltage and sputtering crap.

 

[Oldsid]

I am having a voltage drop problem that I am trying to fix and when I measured the voltage on my battery, it was 11.9V at idle! However it was still pulling at 4000 RPM before I did the voltage check and did not seem to affect the fuel pump at this voltage. I hope you'll find the cause of the problem soon.

 

[One Equals Two]

I think I have somewhat of a clue now, and it's one of those "3 things went wrong at the same time" problems, making it very hard to trace.

One, at first everything points to me that there is a bad ground or a bad alternator. But, I've eliminated that already. However, I redid the battery terminal cables today and gained .3 volts, so I am now at 13.2 volts BUT, it doesn't vary with any load whatsoever. 4000 rpm with no accessories on is the same voltage as 900 rpms with all accessories on. 13.2.

Well, I read again a recent thread where the guy said his ECU was bad and that it was a circuit on the ECU. My problem is, is that when I turned the car on, I realized that the ECU was working (CEL came on when leaning out, etc.) so I assumed it was fine. But the problem is is that it may actually only be partially broken. Meaning, in the resistor that went out in that guy's (other thread) car, was also the resistor that is in charge of the A/F ratio circuit?, which would explain why my car is leaning out so badly. I found a guy who is willing to let me try his ECU, so I'll post results later today.

 

[Alex Bland]

check the resistance between some of the alt lines and feel a cupple lines with car running or something see if any of the lines get really hot. if so replace that wire

 

[One Equals Two]

Well, the guy got tied up, but there is a clue in that the main ground wire is hot. It looks like the ground points are good, but the wire may be shot.

Question: Where does the main negative terminal ground usually go to? I see it go into the wiring harness, but don't see where it connects to.