MA7008O

I know that it may sound silly, but I am confused with the 3 cables that attach to the back of the alternator.

• Bigger size wire, red color: no problem, to the large nut.
• Medium size wire, undetermined color: which side, to the smallest nut close to the large one or to the Phillips head machine screw. Is this wire “ground”?
• Small size wire, kind of green color: which side, to the smallest nut close to the large one or to the Phillips head machine screw.

Thanks a lot for your kind help.

Rocket Rob

Brown is ground. The Green is the alternator field excite wire. The green wire goes to the post near the big wire. The ground goes under the smaller screw.

Do not reverse it with the ground wire. I accidentally did and it damaged the alternator diodes. When I corrected it, the faulty diodes then damaged the engine wire harness.

MA7008O

Thanks very much. The picture is perfect.

cobias1

Rob, how long did it's take before you realized the damage on the diodes? And did the alternator charge initially?

Rocket Rob

After correcting the installation mistake, I took the car for a test drive for about 10 minutes, on the way home, my radar detector began rebooting continuously. I made a bee line to home and the engine died as we coasted into the driveway. Honestly, I can't remember if the we checked the battery voltage at first or not. I suspect we did.

cobias1

Do you remember how long before you caught it?. Might be why mine are blowing.

Rocket Rob

It was 10 minutes of driving.

cobias1

I guess my question was somewhat misleading..I was wondering how long was it incorrectly connected and how did it run/test out in that fashion. sorry for any confusion. Reason im asking is that as we talked about from before I keep blowing the alternators and the shops getting tired of replacing them. I wondered after reading this would I still be able to run for some time ( a couple of weeks ) with the wires incorrect before blowing the alternator. Hope this makes a bit more clear what and why I was asking these questions.
Dan

Rocket Rob

Now I understand. I had my wires in the "wrong" position with the engine idling for about 45 minutes. The car stalled with a dead battery. When we realized the mistake and pulled the alternator to correct the wiring. Started the car, checked output voltage. Celebrated the success by taking the car for a drive. On the way home, I realized it wasn't charging. When we got home and removed the alternator and we saw the wire harness was burned. There were 6-10 inches where the insulation was burned off. Some wires were so over heated that the conductor broke.

I was amazed at the damage.

cobias1

wooohoo..kinda sorta, finally found out that the reason im blowing alternators is a bad wire in the engine wiring harness loom somewhere. The trackdown begins tomorrow. I'm sitting this one out because electrics arent my thing and two gotta work next couple of nights. just hope the bill teeters toward the easy side of life and they find the break in a reasonable time.

Rocket Rob

Glad you are narrowing in on the fault. Keep us posted.

cobias1

Heya rob, update is not change this week . May go pick up the car next week and take it home and see if I can try and track down the wire myself .

RicardoD

&*$&*(Q&#*@!!! I just got my engine started after my big reseal job and the alternator light came back on because I flipped the green and brown wire just like Rob did. At least Rob saved my *** now and I know to fix the alternator diodes before hooking it back up properly again.

Rocket Rob

Ricardo - Sorry to hear you made the same mistake that I did. In hindsight, I wish the factory or Bosch had put unique sized connectors on those alternator wires, so that it would be "dummy proof".

Definitely get your alternator checked before trying it again.

RicardoD

I got my alternator checked at the rebuild shop this morning. Autolectrics They did a quick check on their test bench. Everything is working fine on the alternator so I can hook it back up the right way this time. I didn't damage it but am very glad I checked.