When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have an 05 Ranger with 4.0 engine. Lately if I punch the throttle to pass, or the transmission kicks down going up a hill, the battery light will come on until the rpm's drop back down. Good battery, clean tight connections, tension on belt is correct. Any ideas what's going on?
Suggest you get the alternator tested, though at 3 years old it should not be failing. Consider my experience in the thread below and the excellent feedback I received from the members.
Sounds like the alt maybe bad. Take the truck to the local auto parts store. Most of them do alt test for free. I wouldn't suggest using autozone though. I have had really bad luck with there alt in the past. Might get 2 or 3 from them before you get a good one.
I've seen quite a few alternators go bad in a way where voltage drops at high RPM's.
I think this is probably your case.
I've seen a lot of aftermarket alternators for these that had the incorrect Regulator installed. They will plug in and charge just fine, but will cause the BATTERY light to be illuminated. Motorcraft is your best choice, but it can sometimes be cost prohibitive.