You mention being a Ford guy when Chio said the ECU controls the alternator. Yes, that's the Engine Control Unit. It has a control wire to the alternator & it can shut down the alternator by grounding that wire.

There's an elecrical load detector (ELD) built into the fuse box. When the battery voltage is good, and the ELD indicates little or no electrical load, the ECU will signal the alternator to shut down.

But... if that signal wire has its insulation rubbed off, & shorting to ground, THAT will also tell the alternator to shut down. I don't have a '91 repair manual so I can't tell you what color wire that would be.

 

the saga continues. I downloaded the manuals recommended above. after pouring over them i found that there are four things that control or affect the alternator output.
the regulator in the alternator
the ECL in the under hood fuse box
the Integrated Control Unit above the fuse box behind the drivers side kick panel
and finaly a small 4 wire relay located above the glove box on the right side of the car.
Well I pulled the relay and it tested bad. no ohms or continuity. took it to the auto parts store they had no listing at Advance or NAPA..local store called Bumper to Bumper had one on the shelf. Bingo everything is fine YAHOOOOOOOOOO!!!
Thanks for the help guys. I love forums.....

 

Thanks for posting the fix. Glad your problem was solved!

 

I know this is an old thread but does Anyone have a clue what the relay is called this guy replaced? I'm having the same symptoms with my 94

 

Check that alternator control wire mentioned in the earlier posts in the thread.

Just because his was a bad relay, you should go through the process of ruling out the more common reasons because it's likely yours is not exactly the same failure.

91 & 94 are different generations of Accord, so your alternator control circuit might not even be the same as his.