I ran a nice and shiney bosch alternator for 3 years and it decided to explode (yay, brush explosion!). I had to very quickly get a replacement and the fastest way to do it was snag an ultima alternator from orielly's. Turns out, it's ultima crap and I am having to exchange it today. I also had to buy a new battery because when the alternator failed, it failed to light up the charge light.

When it failed, these where the readings...

L= 14.6v
S= 12.92v
B= 14.53v

From those readings, it tells me that the internal regulator failed. From what I understand according to the S5 wiring diagram, the S wire is what charges the field coil. L wire controls the light on the dash so that explains why it's not lighting up, and if B and L are about the same voltage, the charge light won't illuminate. It seems the diode trio per the S5 wiring diagram burned out, so the alternator is trying to charge but taking the field coild coil charging current from the battery instead of from itself.

If I am wrong in my conclusion or if yall have any other information regarding the situation please tell me. Hopefully replacing the alternator fixes it.

 

So new MT-35 battery from Interstate installed, new alt installed and everything is normal. Before I changed out the alt, the old alt was sucking the life out of my battery like a vampire. For example, before I swapped alternators, I started the car and with no extra loads (lights, radio, etc) The battery voltage went from 12.52v to 10.3v instantly.

Put the new alt on, and everything was fine, even fired up the high beams and set the blower to maximum, still good to go. I still want to do some measurements today with the multimeter and post them.

The new alt makes the belt whine at idle, so I know it's slipping. So I guess today I finally get around to putting on the new belt I bought 2 months ago...lol.

 

Alt belt replacement...(let's hear it People..he's gonna DO it!)

 

I did it and now my air pump belt makes noise.