2G Alternator Issue

[tay97gst]

Hey guys,
So I dropped off my car to get dyno'd last week and when I got it back I noticed that the voltage was low (have a voltage gauge) while the car was running. I figured that something happened with the alternator during the dyno tuning so I went ahead and got a reman 90 amp alternator and threw it in. But the voltage is still very low while the car is running.
I should mention that my battery is in the trunk so the alternator charging wire has its own dedicated line with an in-line circuit breaker going directly to the optima red top battery.
I checked voltage at the positive post on the alternator, when its off it reads 11.3v (not surprised its that low considering the alt hasnt been charging the battery) and it reads 12.0-12.1 while running.
The fusible link in the fuse box appears fine and the circuit breaker wasn't tripped. Also the battery light comes on with the key in the on position and then goes away when on.
Whats confusing me is the fact that the brand new alternator is only reading 12v at the positive post on the alternator. I would think if it was a fuse or something weird in the wiring that it would read 13-14 at the alternator and then break somewhere down the line to the battery. Does this make sense to anyone?
The battery has been relocated for probably over a year now and I havent had any issues before this. Let me know if you guys think of anything because I'm kind of at a loss right now. Thank you

 

[GRAVEDIGGER]

I would say that your alternator is junk. Not uncommon at all to have a reman alternator not perform right out of the box. You are understanding correctly and if you are not getting at least 13.5 volts then the alternator is not doing its job. You need to have 13.5-14.8 volts or so on a good charging system. If it is at 12.x volts, that will not work, period.

 

[tay97gst]

I would say that your alternator is junk. Not uncommon at all to have a reman alternator not perform right out of the box. You are understanding correctly and if you are not getting at least 13.5 volts then the alternator is not doing its job. You need to have 13.5-14.8 volts or so on a good charging system. If it is at 12.x volts, that will not work, period.

It could be a bad reman, but I'm also wondering something else. I'm pretty sure the 2g alternator has a low output mode and a high output mode, controlled by the ECU, that changes given different load types and rpm and whatnot. Im wondering if for some reason the alternator is stuck in low output mode for whatever reason. I ordered a new generator relay for the alt which I should get tomorrow so I'm going to try that first. Then if that doesnt work I'll get the new alt load tested and see if it passes or fails. If the alt passes then i'll have to assume something strange with the ecu is going on.

 

[GRAVEDIGGER]

Then if that doesnt work I'll get the new alt load tested and see if it passes or fails. If the alt passes then i'll have to assume something strange with the ecu is going on.

Not so fast... I have seen many alternators pass when tested off the vehicle, but they fail miserably back on the car. The on car test is the most reliable.
As for the high/low mode controlled by the ECU, I have never heard of that. There is a voltage regulator built into the alternator and that's it's job.

 

[tay97gst]

As for the high/low mode controlled by the ECU, I have never heard of that. There is a voltage regulator built into the alternator and that's it's job.

This is the information I was referring to about the 2g alternator.
https://www.ecmtuning.com/wiki/ecualternatorcontrol

 

[tay97gst]

Well the new generator relay didn't solve this issue, so I'm going to pull the new alternator and get it load tested and see what happens. If it passes i'll check the alternator connector wires for continuity to the ecu and if that doesn't reveal any problems then my hunch is that something is going on with the ecu. I'll report back with my findings.

 

[Matthew Lipford]

Im also having alternator problems, overcharging. I unplugged my 4 pin harness to alternator and still puts out 15.2.. Can you post a pic of the wires to relay and alternator? Thanks.