Gen 1 light on

When I said “plug on alt” I was testing the terminals that the brown/red plug connects to on the alt. I thought that’s what you were saying to test.

Ok so now that I’ve opened my eyes and I understand you were talking about testing the big red wire on the back and not the plug where I removed the red and brown wires, I’ve figured it out. The alternator was bad and the only reason barrmans protocol want working for me was because I was confused. Feel free to put this to bed.

Looks like what I would expect if Gen1 isn't charging. Red wire is voltage sense - it tells the alt what the voltage is at the other end(usually a junction terminal). Brown is the wire from the light. 12v is expected when the key is on but engine not running. Current goes from the Gen1 bulb (12v) into the alt (at low volts) causing the bulb to light. When the motor starts, the voltage on that terminal should go to 12v once the Alt starts charging, balancing the 12v at the bulb and with matching voltages, the bulb goes dark.

Might be time to pull Gen1 and check the brushes. Bad brushes = no rotor current = no charge.

I had a spare alt and I've swapped it, solving all problems. I'll buy a rebuild kit and rebuild the bad one so I can keep a spare.

Glad you got it figured out. After I wrote the above I went out and looked under the hood of my m1009 to make sure I had the wire colors correct.

Something about the back of the drivers side alternator didn’t look right so I touched the bolted on red wire. It moved. So did the stud in the alternator. Which caused it to short out, make big sparks, lots of smoke and a few burned up fuse able links on the firewall. Yeah. Good thing I bought a 10 foot roll of fuse able link wire years ago when I first got a CUCV.

Time me to use my spare rebuild kit I keep on the shelf for just such an occasion.

Barrman said:

Good thing I bought a 10 foot roll of fuse able link wire years ago when I first got a CUCV.

Click to expand...

Yikes!

Good thing it happened at home, and not driving down the road, or at a stoplight, or across town somewhere.

One question, I have a 12v alt output red cable with the key off and on,

In the upper red/brown connector I get with the key off:

red 0v
brown 0v

with key on
red 0v
brown 12v

The car's voltmeter shows 28v charging, but the Gen 1 and Gen 2 lights have stayed on.

The bulbs are correct 168 and 194

and fuses ok