Been searching for hours...I can find info on testing 1G and 3G stuff, but jack all on 2G stuff other than "it's junk, replace it with a 3G" or "full field it, if it makes voltage, your regulator is bad and replace it with a 3G". I get it..2G alternators have issues. But I bought this van a couple months ago knowing it had charging and cooling issues, got seriously ill immediately afterwards, and haven't even driven it except on and off the trailer. So right now I just want to get it driveable as cheap as possible so I can verify that it IS just a faulty alternator and dirty radiator like I suspected, and not something serious like a trans in need of rebuild, blown rear end, bad engine, etc.

'87 E350 RV conversion, 460 motor, internally regulated alternator. No output with engine running. Verified battery voltage on the two large battery wires on the "fire plug". Verified continuity between the stator wire on the fire plug and the other 3 pin. Verified battery voltage on the A terminal, and I terminal wires.

Brushes were worn down to about 1/4" long, but I could get 16+ volts off it with the regulator test screw grounded just by running it off a drill while hooked up to a battery on the bench, while wired the same as it would be on the van. Was 99% sure the brushes weren't the problem, but they were $4, so I replaced them anyways. Still getting no output out of the alternator without grounding the test screw. So it _looks_ like a faulty regulator, but I want to be SURE of it before replacing it.

Pulled the regulator, grounded the base. Put 12V on the A terminal with an adjustable power supply. Ran a 12V bulb in line with the I terminal to simulate a dash bulb. WIth power supply on at 12V, I'm getting 6V off the S terminal that stays pretty steady from 8V to 16V from the power supply.

Bought a new regulator, and getting the same exact thing. Of course, it's possible that the new regulator is DOA, or also possible that I fried it by wiring/testing incorrectly. Did I wire it incorrectly for testing? Do I need to simulate the presence of the armature for testing?

 

The armature is what the regulator is controlling. Which is the same thing as the field in the older alternators. Hard to test that really. When you full field the alternator, you are putting 12v on the armature. Why not put the new regulator on the alternator and see what happens when the engine spins it.

 

Multiple reasons. I'm not a "throw parts at it and see what happens" person. I prefer to fully diagnose, then replace as needed. Especially when it's a $60 part. That's often a good way to spend multiple times over what it would have cost just to buy a whole new assembly.

It's also a learning experience for me. I haven't dealt with a regulator of this type before, and I'd like to learn exactly what it's doing if the need ever arises again in the future.

Oh, and it's a major PITA getting the alternator in and out of these vans. Ended up having to pull the air pump and bracket holding the air pump and alternator off the motor, then dropping the whole mess out the bottom, because the alternator pivot bolt doesn't clear the radiator. The fewer times I have to go through that, the better.

 

So it was the regulator...

I did some more playing with the two, and the "12 volts on the armature" that I didn't think about earlier. Wired them both up the same again, and noticed that as I increased the supply voltage, the old regulator matched the voltage up through 17 volts on the brush terminals.

The new regulator however cut voltage to the brush terminals right at 14.5 volts, so feeding the regulator 15 volts caused the brush terminals to go to zero. Once the supply voltage lowered down past 14.5 volts, the brush terminals turned back on.

I suspect that had I put a load on the brush terminals of the old regulator, I likely would have seen it drop considerably below supply voltage or drop altogether, but I ended up tossing it before that thought came to mind...oops.

Regardless, popped the new regulator in the alternator along with new brushes, reinstalled it, and the dash gauge immediately registered charging upon engine start.