I’ll try to be as detailed as possible.

Car is a C6 2006 LS2 with an A&A kit, fuel system, cam, 10% OD balancer, all the good stuff.

One night on a drive my alternator pulley came off. I then replaced the alternator with a brand new upgraded unit (250amp). After a few runs, i got a service charging system message. Drove home & checked the damage in the morning. I realized the alternator seized. The pulley that was provided with the new alternator was too small, and caused overcharging which fried the alternator. I sent that unit out to get repaired on warranty. They replaced a bunch of stuff inside including the pulley. Bench tested and charging as it should.

After that new unit was installed, with a new battery, big 3 kit from sac city, the alternator wont charge the battery. i start the car, it will go to 14.4 but then after a minute or so, drops down to under 12v.

I checked every single ground, i checked idle voltage at the alternator post and then battery post (both read under 12v), i inspected the fusible link at the starter, i checked the horn fuse, i swapped out my spark plugs, i even double checked any wiring i have messed with at the tail lights and side mirror led’s just to be sure, no luck.

I’m stuck and have no idea where else to look or what else to do. Any direction or advice on what i should be doing next would be very much appreciated.

 

some alternators are not compatible with C6, even they said they are. it has something to do with which component is doing the job of voltage regulation. if you search the forum, you can find some related topics. through, this may just be one of the possible causes for you.

 

Yes, you want to make sure you have the right alternator for the car by giving your local Chevy dealer your VIN and see what it is…is it OEM or aftermarket ??…where did you buy it ??….HOW exactly did you check your grounds ??…you don’t have to check EVERY ground but only the ones that may be associated with the charging system…you are just wasting your time…do you know how to perform a voltage drop check on the charging system ??

 

this is an aftermarket alternator from Js alternators. 250amp. I checked connections on both ends, making sure the wire itself was intact as well as solid surface where it’s bolted to. I don’t know how to do the voltage drop check, i just checked voltage at the alternator post and battery post before and after the voltage drop at the gauge cluster.

 

To do a voltage drop check put an electrical load on the alternator and run the engine at 2500 RPM…put one lead of voltmeter on alternator B+ and other lead on battery positive terminal…shouldn’t see more than 0.5 volts…to check negative side of charging system one lead on alternator case and other lead on battery negative terminal…shouldn’t see more than 0.5 volts…this is what I see on my car 0.32 on positive side and 0.10 on negative side.