Alternator slowly not charging

[awwphooey]

Hello folks-

Any help on this would sure be appreciated. I have a 1996 4 cyl Ranger. Issue is, I was driving to work and the ammeter indicator started wiggling around. It started dropping, and when I revved the engine, it would pop back up- but eventually, even that wouldn’t work and it died. I was stuck without my tools, so I got a ride to the local Walmart and dropped a new battery in. Made it home, but the same thing happened as I pulled into my driveway.

Charged the battery, got out the voltmeter, battery is at 12.4 V when not running, started the engine and started at 14V, then slowly over 3 minutes with lights, AC and radio on, dropped down to 11V. Turned off engine. Took alternator out and had it bench tested at NAPA. They said it was fine. As a test, went to a Ford salvage yard and picked another one up that was also tested fine, put that one in. Same exact issue.

Checked all my fuses, the box in the engine and the panel in the cab, everything checks out fine. Seems that the alternator charges fine for a bit, then drops. At the top of the morning, I can drive for about 20 minutes before the voltage drops.

Any thoughts? Thanks in advance for the help!

Phoo

 

[xkotyx]

sounds crazy.
ive had the auto store test things before and show up fine, but switch them anyways and all of a sudden work. i guess they still worked, but were just too weak.
but yeah, sounds like something more complicated.

 

[nitrofan1]

Rule of thumb: Fuses pop they are dead so eliminate those. Relays.....eh, pretty much the same. I would look at faulty wiring, dirt or corrosion at the regulator plug, crappy grounds, diode pattern in the alternator and even insulators on the harness going to the regulator being frayed a little.

Best bet before throwing a lot of money at the problem is have it diagnosed with the right equipment. You may find a simple solution by diagnosing it. I had a charging problem a few weeks ago. Took a short finder and found frayed insulator covers on the regulator plug about an inch from the plug.