Update .
today I tackled the lower alternator. I pulled the entire harness from that area. I had 2 glow plug wires for the front most 2 glow plugs coming off the bottom of the main harness, then the pink and green for the injector pump. Then what looks like the main harness ends in the top and bottom alt harnesses. These were both connected to the bottom alt. I removed and taped what should have gone to the top alt ( yellow, white, black with white tracer). The bottom alt harness has 2 reds (1 in the harness and 1 going to the 24 volt buss that was spliced in the middle), 2 Browns (1 with a ring connector the other is cut).
I basically taped all of it except the 2 Browns. One is what I hope to be an ignition wire, the other I don't know. Neither has voltage with the key off, on, or with the truck running.
the top alt positive goes strait to the front battery and is grounded to the engine.
the bottom alt positive I ran new wire to the 24 volt buss, and it is also grounded to the engine. All of this is 2 gauge wire.
while messing with all of this my right headlight stopped working, but my low coolant light now goes out like it should. My 24 volt gauge still doesn't work and the 10 amp fuse that powers it is good.
I do need to evict the gremlin from under the dash.
my question is concerning the 2 brown wires. What is the extra one and shouldn't the other show voltage with the ignition on? 12 or 24 volts?
Both alts are grounded to the the engine and the engine is grounded to the negative buss, should I run an additional ground directly to the negative buss?(as seen in the schematic)
Each battery reads 12.7 at rest. the top alt ( plan b mod) is charging at 14.3 volts. The 24 volt buss, both batteries, and the bottom alt positive reads 27 volts, and the rear battery reads 12.7 when the engine is running.
can I jump 12 volts to the lower alt ign spot to see if this will excite the alt?
sorry for all the questions and thanks for any help