Hi there. I've got a 92 b250 with a rebuilt engine that won't charge at all. The alt and battery have both been removed and tested and come up in perfect order. The voltage regulator has been swapped three times with no change to the situation. You may ask "but the 92 b250 doesn't have a voltage regulator" and by all the literature I've found you are correct; this has one and I don't know why. I have taken off and cleaned every grounding terminal I can access; I have continuity from the alt to the battery on both ends; I have bypassed the reg to try and full-field the alternator; I have given up entirely and taken it to my mechanic who is as stumped as I am; at this point I am genuinely considering sacrificing livestock in this thing's name to appease it in the hope that that'll get it working again.

Here's how the reg is installed:

The disconnected ground in the pic isn't the issue, I put it back after I saw it in the pic, and that was last week.

I would love any further diagnostics I can try; I am not a car guy, but I can't really afford what a shop would likely charge to make this go away.

 

Looks like everything is hooked up right. Do you have the wires backwards at the alternator?

 

Near as I can tell it would be physically impossible to do that with the way that connector is shaped.

It was working until a few weeks ago, with no changes made to the wiring by me.

 

Is that a relay I see in the lower portion of the pic? Do any regulator wires pass thru that? If they do, I would replace the relay. It can still act like its working right, even though it isn't.

 

Yeah, I tried bridging the relay plug's terminals and actually using a new relay, to no effect. I forgot to put that in the OP, sorry.

 

Bypass the relay, then check and see if you are getting 12 volts to the field windings, and make sure you are getting voltage back to the regulator as well. Gotta be a wiring issue somewhere.

 

I'm currently getting nothing to the field coil posts. Trying to bridge the regulator wires also gives me nothing.

"A wiring issue somewhere" is what everyone seems to agree, but there's a whole lotta "somewhere" in this tub.

 

Think I would rewire it, and skip the relay.

 

That's the plan I had come to for today.

Any idea what this plug is for?


Left rear-ish corner of the engine.

 

Today I replaced all of the wiring between the regulator and the alternator with new, and eliminated the relay. Basically the dead simplest circuit I could create.

Here's what was present before:



And here's what it looks like now:


However, she still isn't charging, even if I bypass the regulator and full-field it.