Charging Issues?

[ZacLoveall]

1997 Reg Cab Ranger 2.4L 4CYL 2WD Manual Trans.

Battery Light on dash came on this morning. Went off shortly after. Has been "intermittent" since.
Light comes on mostly at High RPM. AC was on, tested with AC off as well. (AC also seams weak)

Took it to AutoZone, checked battery, alternator and starting system.
Their little machine said battery and alternator were GOOD, but starting system was bad?

At AutoZone, they "could not" check at high RPM.
Planning to check serpentine belt tension
Planning to check alternator output at high RPM this evening with Multi-meter?

Have a 200mile trip coming up, wanted to see if anyone had any suggestions for other things to check?
Any prep I can do before the trip, so I dont get stranded?

Thanks in Advance

 

[pentode]

Do you have a multimeter? If so, start by checking the battery voltage with the engine off, then with the engine idling, then raise the rpms a bit (2000-2500) and check again and report those numbers back here. I think that's a good place to start.

Edit: I don't know what Autozone thinks a starting system is, but if the battery is good and the starter works, I'm not clear on what they're imagining is bad. Cabling? I discover whether my starting system is healthy every morning when I turn the key and it starts up. Either way I can't see that affecting your charging system, which is what the battery light should be telling you about.

 

[ZacLoveall]

Tested with Multimeter - From BAT POS. to BAT NEG. (also checked just ground to engine)

Engine Off - 12.95V
Engine Idle - 14.12V
Engine High - 13.02V

Using OBDII Scanner (BC no Tach) at 3,000ish RPM - Battery Light comes on, and Voltage across the battery drops, also engine temp rises and ammeter gauge drops. Thinking possible serpentine belt slippage.

Also, agree not sure what autozones scanner was checking for.. but she starts up fine every morning! HAHA, I guess I was just adding as much info as I could, because I had read something about fusible links from the alternator.

 

[pentode]

How bad is your belt? Unless it's shredded I wouldn't expect the voltage to drop as rpms rise, I'm thinking voltage regulation.

BTW I wasn't questioning you about the starting system health thing, I was just thinking "another greasy way to try to scam a few more bucks out of people" by one of these stores. But I'm famously cynical.

edit: battery sounds very healthy. Alternator can clearly make voltage. I don't know if the regulator can be replaced separately on this alternator but my shot from the hip is failing regulator but I would think it's an unusual failure.

edit2: looks like it's replaceable and looks like yours might have a lug you can ground to test the regulator

 

[ZacLoveall]

HAHA no worries, No offense taken lol!

belt seems to be in okay shape? (pics for reference) - Belt tensioner seems to be pretty sticky. (doesn't seem to spring back)

going to dive into how to test regulator as well!

Thank you for the responses!

 

[pentode]

yeah, if the belt isn't super dry or cracked and you don't hear lots of squealing and screeching, I think you can rule out the belt.

My money is on voltage regulator but I'll be happy if someone checks in and tells me why I'm wrong. Also, I'd put good money on you making your 200 mile trip no problem, assuming you're driving in the daytime and it's not 200 miles of highway. It's charging sometimes. Seems like when the voltage rises to a certain point it cuts out.

 

[ZacLoveall]

Went ahead and replaced serpentine belt and belt tensioner - in the name of preventative maintenance and cheap insurance.
that did not resolve the issue!

I believe you still have a high probability of being correct, working through the Regulator low voltage test today!

Will update with results!

Also the 200 miles will mostly be day time, and should be 55mph or les so should be all good! Appreciate the vote of confidence!

 

[pentode]

I'm sure you found this on here: https://www.therangerstation.com/tech/charging-system-general-information-precautions-checking/