On Sunday, May 22, 2016 at 4:19:36 PM UTC-4, Snuffy "Hub Cap" McKinney wrote:
My 97 Ford van has an intermittent electrical problem. Testing the battery under load it seems to be OK. Connections and wires are all good. Now I suspect the alternator.

It's a job to R/R the alternator in this car, so I'll really like to confirm that's the problem first. Simple checks shows it's charging and battery holding a charge, but that's when it's not acting up.

Anyone know where to find a schematic of the alternate? Or a way to get it to show the problem? Most of the time, no symptoms.

This is typically of the intermittent problem.....

At night, with the headlights on, the lights and meter start to cycle very slightly about 2 Hz. One night I had parked and left the lights on for 20 minutes, then started the car and the battery warning light started flashing and the meter needle swinging 0-100% back and forth indicating a problem. I switched to parking light and about 5 minutes later all returned to normal.

Thanks!

I don't remember the years affected, but Fords did have a problem with the connector plug on the alternator. If you can get to it, wiggle it while the engine's running and see if there's any affect.

Modern cars (yours included) are real picky about battery damping. I've seen bad batteries cause weird problems yet still deliver enough current to spin the starter. If you have a bad diode in the alternator it can cause an AC component which drives electronics nuts. If the alternator is original it's 20 years old, so it could be dying.

And as jurb pointed out, check those battery connections first and thoroughly. My wife's Jeep had an intermittent problem that wasn't solved until I cut off the old battery terminals and installed clamp on ones. When that was acting up, it would peg all the gauges and flash trouble lights.