I have a 2008 coupe that has been giving me problems. I have taken to the dealership and local shops and cant figure it out.

The vehicle has a high output alternator and the wire upgrade kit to 0g. I contacted the company i purchased the alternator from and seems like everything is connected correctly.

I believe that even thouu is a high output alternator, it should still regulate the power going to the battery. Ive read that normal voltage coming out should be a bit over 14v and seems to be correct when using a tester. I dont know if thats accurate since the batteries shoould be 12v.

Problem 1: My batteries keep expanding
Problem 2: Vehicle wont go past 3500rpms before it stalls for a couple secs

 

If the battery is expanding (swelling) then it is being severely overcharged.

What zero (0) gauge wire kit? Is this a grounding kit?

Did you bypass the current sensor?

 

Yes, its been overcharging.

The wiring is the grounding it (Big 3). It has the wires from alternator to battery and ground.

I am not sure about the sensor. Where is it located?

Before performing the alternator swap, there was a braided wire (ground strap) that completely broke going from the chassis to the manifold. I tried replacing that wire but seems like it didnt had the power to turn on, until i added a ground wire from the chassis to engine. (See image)

 

These cars use a variable control charging system:


It appears that your setup is causing the alternator to charge at a constant 14+ volts. This could be due to a bypassed/ faulty current sensor, improper alternator setup, the grounding kit, etc. Some cars had issues with grounding kits and these cars. Some love them, others not so much. See this thread.

The current sensor is attached to the negative battery cable between the battery and frame


Is this alternator specifically for the G or is it a aftermarket unit that is being "rigged" to work. In other words, why did you switch to a "higher output" unit as opposed to the OEM unit? Do you have additional mods pulling more power, like a audio system?

 

The alternator is aftermarket by JD Alternators which should be designed for the G37. The reason was because i qas getting a lost in power and felt like battery wasnt handling even brand new batteries. At the time i believed it was the extra power being drawn due to audio system, aftermarket lighting, and the air pumps running for the air suspension.

And yes, the cable in the image you provided is attached to the battery.

 

But is the current sensor (the donut-shaped module) attached to the cable and is the wiring harness connected to the sensor?

My guess is that there is a issue with either the current sensor or the voltage regulator in the alternator.

Perhaps others will have more ideas.

 

Yes, it is connected. My guess will be remove the alternator and the Big 3 and operate with the original OEM one without connecting any electronics except the air suspension. Im just out of other options.

Image of wire

 

In your opinion, would that also be the problem why the car wont go past 3500rpms?

 

With these cars, when it comes to voltage discrepancies anything is possible. Typically, when a voltage regulator fails you experience a "low charging" condition which can trigger the battery AND brake light on the dash to turn on. Or, in the case of a bad ripple diode, your interior lights will "flicker."

In your case, as your voltage regulator appears to be stuck "over charging," I do not know if the ECU has any type of fail safe (ie. limp mode) to protect itself.

The FSM has a pretty detailed diagnostic chain that you could look into. For example, it states to check the 10amp fuse on the battery positive terminal and also to check the wire at the "S" terminal (this is the signal wire that commands the alternator to charge).

However, as you have a aftermarket alternator, I do not know what type of voltage regulation they are using.

 

Ok sounds good. I'll give it one last try. Otherwise I'll take the alternator to test and discard that regulator as a problem. Then remove the big 3 and put OEM alternator.

 

I just noticed this... what did the dealership say? Did they put the CONSULT3 (Nissan scanner) on the car?

 

Man, they weren't even helpful at all. They claimed they couldn't find the problem, after their diagnostics. They told me to put everything back to stock (remove the alternator/big 3) and bring it back.

 

Yep, they screwed you, With the CONSULT3, they could easily test the integrated (voltage) regulator, ripple diode, and whether the regulator is varying output based on demand. Like many dealerships, they don'r want to bother the minute they see anything aftermarket (been there/ done that).

Good luck and please keep us updated.

 

Sounds like a plan. I always say it, a shop on the streets with no type of certifications do better job. The problem is that depending on the type of mechanic, they can be less careful. I like to take my car to shows and hate when they scratch or break stuff.

 

If the engine RPM is limited to 3500 RPM, that means there is a problem with the VVEL system or VVEL/ECU communications.
(As per the Fail-safe section in the FSM)

Have you measured the voltage of the battery with the car at idle? Typical voltage is high 13 to 14 volts
If it is overcharging, it can only be the alternator.