Alternator wire test, and trace Question

[Rasp1980]

1st off I am truly humbled by the amount of knowledge on this site. I have been able to fix several small common issues by reading the many on the posts. So I have traveled down the path set out by fellow members regarding alternator issues. In my case it is the GEN 1 or driver side alt. I have the following symptoms.

No gen1 light at start up no headlights… but I do get high beams. No heater or fan. Which I think is linked to the alt issue but I’m new to the M 1009 electrical demons.

My actions

Disconnected the plug on the GEN 1 alt. Tested red wire with key in off position get my 12v so that is good. (Grounding millimeter to the front battery ground)

However this is where I think I am making some kind of mistake. I go to test the brown wire with key in the on position and I get 66.5V (grounding millimeter to the front battery ground) I did this several times. How is this possible? I’ve got to be making some sort of childish error. So as I’m sitting there staring and disbelieving the meter for the tenth time trying to work this out for myself. I hear a relay some ware in the truck do a 1-2 second single click. And now my voltage is at 10.5

So I’m a little confused and would like some advice as to possible places to look.

What I would like is a little how to on tracing wire demons down. I’m not the most electrical savvy person and am mostly self taught

Does this electrical anomaly mean that my Alternator might be good?

 

[Warthog]

Replace the heater fuse at the top of the fusebix. It controls the heater AND the GEN1 exciter circuit.

Read and print off the first few pages of the trobleshooting section of the -20 or -34 tech manual. It tells you how to read the wiring diagrams.

Your 66v is a problem with you voltmeter. Have you ever replaced the battery in it?

 

[Rasp1980]

Thanks, I will print off the pages and check the fuse 1st thing in the morning. I will update with what I find.