I have a 2006 z06. Keep getting service charging system. Last November I got a mechanic s series bullet 170 Amp Alternator. Still hasn't fixed it. Right from a cold start it does go to 14.2 on a fully charged battery than drops to 13.1 after a few minutes. Than it slowly starts dropping off down to mid 11s after a 15 minute drive. I've replaced the accelerator pedal and added the new wires from the alternator to fuse box and grounded more to the engine. Where do I go from here?

 

did you take your alternator to get tested?
had the same issue a few years ago on my 2007 z06 so no big deal, just go to the auto parts and get a new delco alternator. there i noticed that the pully was a different size so we started pulling alternators out of their boxes and they were all the same, different size pully. so i figured i would change out the pully's and be on my way. wrong! gm changed the pully diameter and how that pully was attached to the shaft. i wanted to keep my size pully so i took the alternator to a rebuild shop and had it rebuilt. same original alternator that is still operating today and this was about 6 years ago.

 

Sounds like the alternator in both cases was not properly grounded, so check that there is no corrosion in the alternator bracket mount points. You could also check the resistance between the alternator case and -ve battery terminal (engine not running). There should be close to 0 ohms if there’s a solid ground. With the engine running, I believe you can check for a voltage drop between the alternator case and ground. If there is one, this would also point to the case not being properly grounded.

 

Voltage reading on the dash, is not telling you the voltage of the dash, but the voltage of the ECM end of line isntead.

So alternator cable to starter solenoid terminal where the battery connects (14.7V), to battery (14.5 volts), to engine fuse block terminal under the hood (14.5 volts) on the positive side.
In the case of a wet sump motor, 14.5 volts from the battery to side off the motor and the ground chassis on the ground side.
In the case of a dry sump motor, just 14.5 volts to the engine chassis about a foot in front of the battery in the back.
Note, keep in mind that z06 has an aluminum chassis, while the surface metal can oxidize as well over time.

Now from engine fuse box on the positive side, to the BCM, then out to the BCM to the BCM (read could have corroded connector pins, and even ground problems. Also to Hence the modules have there own grounds, so problem may not be positive side, but the modules ground sides.

The last one here, the ECM does control the output voltage of the alternator, so problems at the ECM such as corrode pins, bad grounds, or even after market spark plug wires and plugs that are creating RF noise feed back through the spark coils, will cause the ECM to clip the alternator output voltage as well.

Bottom line, electrical gremlins on the Vet is mostly likely either loose connections, corrosion/oxidation problems, or RF noise induced by running non OEM spark wires or plugs.

 

Thanks guys. I have a place to start to try to find these gremlins. I'll also get the alternator checked.

 

A lot of people have had problems with aftermarket and auto part store rebuilds. Best is new GM piece or finding a local rebuilder to fix yours.

 

I just put a Mechman 170 amp alternator in my z06 and I'm getting steady 14.7-14.5volts all the time. Stock was dropping down to mid 12.x volts. I wasn't getting any service messages or anything like that. I just didn't like the large voltage fluctuations (I guess GM designed it that way). I went though my grounds and ran a 2nd 4awg wire directly to fuse box. Machoman's been rock steady so far.

Tips: After everything is all warmed up to operating temp with A/C on plus any other electric load. Go measure the voltage between the following areas.

1: ALT output and mounting bracket (ground).
2: Fuse box + post and ground
3: Rear battery +/- posts.

Voltage should be less than 0.3volts drop of each other. If you have 0.3volts or more difference than you have a wiring issue.

 

My 07 left left me stranded in a construction zone on the Interstate. I replaced the Alt with one from Autozone. Car left me stranded again. Took Autozone crap back and purchased a Mechman Alternator, no problem since.

 

I totally agree with this statement!

Tom