Little bit of an update since memorial day...
I got a new coolant overflow jug in from RockAuto and put it on yesterday. The original bracket didn't like the angled mount of the new jug (old jug mount just went straight up, this one is at like a 45 degree angle), so I ziptied it in a few spots for now just to hold it still and upright, seemed to hold just fine.
I also took the time to unhook the batteries and flip them. I'm pretty sure my GEN1 works and my GEN2 needs some behind the dash troubleshooting, so for now I figure every couple of weeks swap the batteries so that they can charge up on the GEN1 alternator. Prior to messing with anything, the GEN1 light came on with the key and turned off when the truck started (you're about to see why this matters)
Of course, upon flipping the batteries and changing the coolant jug out I caused myself a new problem... my GEN1 light doesn't come on anymore with the key. The truck started, so I know I have the batteries connected correctly, or else it wouldn't have had 24V to start. The fuel pump (12V) and glow plugs (I could hear a change in fuel pump tone when activating the GP) both seem operational with the key in on position, it's just the GEN1 light that's out. Weird. I'm getting a multimeter today, it's due time I dig into charging system anyway...
Full info of what changed: I disconnected the batteries and swapped the battery positions front/back. I replaced coolant overflow jug and removed the original's bracket. When I got the bracket for the old jug off, I found a small ground (I think for the headlight/LED pod light) tucked in behind the washer and bolt that held the bracket to the radiator support. I put this ground back with the same bolt and washer after removing the bracket -- my headlights and turn signals and everything worked fine when I fired her up, I just noticed my GEN1 light was no longer glowing before startup.
Next steps:
1. Maybe the GEN1 light isn't coming on because the "depleted" battery doesn't have enough voltage? -- The batteries are only about a year old, the front battery was depleted from ~20 truck starts. Truck still starts fine and all the 12V accessories still work. Will check both batteries voltage with multimeter. If that's the case and that battery voltage is "low", the GEN1 might not be getting excited and charging.
2. The heater fuse might be out, I have spare fuses in the truck, that'd be an easy test and fix.
3. With the truck running, is she getting ~14.5V at the 12V battery? I'd like to see if it's just a bulb issue and the alternators working fine/the GEN1 light will return after a drive or two.. I doubt I will get that lucky though, dash lights seem pretty critical to normal operation of the alternators...
4. Maybe the bulb died? I feel like that'd be less likely than the GEN2 bulb (which had probably glowed for years when the truck was converted to 12V)
5. Other ideas?
