[RESOLVED] Low voltage from alternator/battery

[b00stedAWD]

Few months ago, I recently relocated my battery to the rear. Everything was ok until past three weeks when my battery voltage started dropping. I'm using 4gauge wire from alternator to main fuse box and 0gauge from fuse box to the battery. Alternator is 150amp, battery is Optima redtop.
Using DMM, car off the voltage is 12.4-12.7 on battery, alternator fuse, and the B terminal of the alternator. I did the same test with the car started. Readings were same 12.3-12.7. So I replace the battery to see if it changes anything and no the outcome was the same. I then replaced the alternator and it still reads same volts. Took the alternators and the batteries to a local auto store for a test and they all tested great. 14.8-14.9v was pushing out from alternators during bench test.
I'm at a loss. Only thing I haven't checked is my Harmonic balancer to see if it split. Like I had mentioned above, everything was fine until three weeks ago. Any input is appreciated.

[dsmmack]

If everything bench tested fine then i'm thinking its a connection in one of the wires, not positive, but that could be the only other possible problem if everything else was tested and everything was fine there.

[b00stedAWD]

I don't think it's a connection problem. I've measured voltage from three different locations and they read .1-.3 from each other.
Does anyone know what the 4 wire plug is?

[dsmmack]

Have you tested the alternator while it is in your car to check its output?

[b00stedAWD]

Yes, While the car is at idle the voltage from alternator B terminal reads 12.4v. I've tried this with two other alternator and the voltage read the same. Took all three alternators to get bench tested and all three shows 14.5 to 14.7 voltage output.
Tonight I've brought the battery back to factory location to see if my wiring was causing this problem, but the problem is still there. It seems like something is not telling the voltage regulator to start charging. This really sucks. By the way, thanks for responding.

[Prodigyman]

I have exactly the same problem and went through 2 alternators and now have Optima Red top and all of them work just fine when car is cold it goes to 13.8 and then slowly drops down to 13 volts and stays there... I have no idea would could cause this problem and at a loss here myself.

[b00stedAWD]

Sorry to hear, I still haven't found a cure.

[DSM_PWR]

check the "Generator Relay" its the relay thats bolted down right next to the stock wastegate solenoid, its the cause of "Most" charging issues...

99 Year models dont have it for some reason but 95-98's do. Mitsu charges $30 or so for a replacement

[b00stedAWD]

I've replaced that relay and the problem is still there.

[16g-2ndgen]

have any of your wires corroded? have any of your grounds came loose?

[b00stedAWD]

I completely re-did my harness. I didn't cut any, I just cleaned it and reloomed. Added extra ground wires.

[danielbui]

We found out we had a Faulty Tensioner on the Timing belt. We got lucky the car never did any dyno pulls or 1/4 mile runs. Just start up to base line tuning.

[pneumo]

How would a faulty timing belt tensioner cause low volts?
Or do you mean a loose alternator belt tensioner?

[spectr019]

I had a shop change my timing belt a few summers back, and when they called me to tell me that it was done, the car wouldn't would immediately stall out. They tried to tell me that it was because of my fog light wire being open, that eventually it corroded and somehow cut into the rest of the system...soooo haha nah, I had them redo the entire timing belt and to their great surprise, it worked. So yeah, something on the timing belt/balance shaft belt/that area can cause havoc if not properly installed.

Ben

[havoc742]

Had the same problem on a toyota. Found out it was the IC Regulator. Not sure where it is or if the DSM has one.

[Car Cannibal]

Try reading the volts at a higher rpm, it's possible the alternator isn't up to snuff at low rpm's but around 1100 and higher it's pumping out the proper volts, I'm there again on alternator 4 and it will eventually crap the bed on me while driving again.

[damnslowtsi]

It is a normal operation of a voltage regulator inside the alternator to pump out less volts when the underhood temps go up. I 'm not saying though that it is normal for voltage to drop to low 13s - high 12 volts. Oftentimes those refurbished alternators use cheapo taiwan voltage regulators that cause problems like that.

[pneumo]

Originally Posted by damnslowtsi

It is a normal operation of a voltage regulator inside the alternator to pump out less volts when the underhood temps go up. I 'm not saying though that it is normal for voltage to drop to low 13s - high 12 volts. Oftentimes those refurbished alternators use cheapo taiwan voltage regulators that cause problems like that.

Yes, I've noticed voltage drops by around 1/2 volt as temps go up.

[andy4g63]

Yes it absolutely normal for the voltage to drop around 0.5-0.8V, when the car really gets hot. I have AEM and watching that on my Greddy TT, it is like that all the times.
But my voltage does not go below 13.4-13.6V.

[danielbui]

because of the heat we are relocating the Alternator the firewall location and deleting the AC.

As shown in this pre-installation photo the 3inch exhaust opening is aim directly at the alternator and once we put the Downpipe on It was about less than half an inch away from the power lead to the alternator.



We wrapped the Downpipe with Thermal wrap but it just seems to be a little TOO hot in this area of the engine bay for us since this vehicle is driven daily.

[andy4g63]

Yep and if you don't relocate it the alternator goes BAD in no time, just from the heat. Happen to me in a little over a year and the car is driven just once or twice a week, but not for commuting.