Yes, another Gen 1 question

[aaron1009]

I apologize in advance. I troll around here and contribute when I can, so I'm familiar with how often these types of questions are asked. Stay with me.


I've looked over the TMs and even a diagram that a prominent member put together and linked in another thread but can't quite figure this out. Probably a simple answer. Here we go.

Short version: Lost my Alt 1 belt. I replaced the belt and am not seeing 14.4v from the back of the alt. Tested the two-pin connector and it acts as if it should (12v on red, 0v on brown with key off. 12v on red and 12v on brown with key on). Key on, no Gen1 light, Gen2 is lit. Running, no light on either. Is this normal? Shouldn't the Gen1 light be lit since I'm not seeing proper voltage?

Long version: Transmission line into the radiator sprang a pinhole leak, which almost certainly covered the Alt 1 belt, causing belt slippage and wear. During a previous alt rebuild, I managed to knock the back out of Alt 1 while trying to hammer the bearing out of the back (yes, I know...). I found this piece, which I had JB Welded back on, laying on the frame rail when I parked the truck. Lucky, lucky, lucky. Of course, I "JB'ed" it back on, and put on the new belt on once it had set. I'm afraid that without this back portion of the alt that perhaps the shaft had enough wiggle room to damage something inside. I haven't yet had an opportunity to pull it and see. That's the plan for tomorrow.

EDIT: For clarity, I found the snapped belt as well as the back portion of Alt 1 in the engine bay at the same time. Same occurrence as the transmission line leak. Huge cluster all at once.

So, am I missing something simple? Yes, bulb has been checked.

 

[ryan77]

I would buy a new Alternator and be done with it! CUCV electric has them!

 

[aaron1009]

I would buy a new Alternator and be done with it! CUCV electric has them!

If I was certain that the alt just happened to go bad when the belt came off, I'd be on board with this idea. My luck dictates that I'd drop the cash on a new alt just to put it in and still have a small issue somewhere else that could have been resolved to get everything working fine.

 

[mistaken1]

The Gen 1 light needs a ground connection (through the alternator) to allow current to flow.

Do you have voltage on one side of the gen 1 light?

If so then you need a ground on the other site to get current to flow.

From here:
Understanding Alternators, How Alternators Work

WARNING LAMP

This brings us back full circle to the starting point - the alternator warning lamp. As can be seen from figure 5, a schematic for an actual alternator, there is a path to ground from the field current supply input [1] to the regulator. As a result, when the key is turned on, current flows through the warning lamp, through the resisters, transistors, and field coil, and then to ground, causing the lamp to illuminate. Once the alternator is at full output, voltage from the diode trio, also applied to [1], equals the battery voltage. At this time, with 12 volts on both sides, the lamp is out.


If that is a stock military unit then it is isolated ground and needs the wire from the ground terminal to the engine block. Since part of the case fell out there could be damage to internal wiring or a loose internal connection (assuming that external ground connection is good).

 

[ryan77]

If you put a test light in the alternator plug, does the gen light come on? If it does your wiring is good and the alternator is bad!