Hi, newbie here. I have a 98 ranger with 2.4 engine. Not sure how to interput an elect. problem. When the truck is at idle, lights on heater fan on high everything is fine. When I drive and build up rpm's the lights dim, fan rpm's drop and the battery dummy light comes on. When I push in the clutch and allow the rpm's to drop everything returns to normal. At idle the alt. is putting out 14.4 at a higher idle when the lights dim the output is 11.4 to 12.6. it bounces around. Not sure if it is an indication of a bad alt.

Any feed back would be great, Thanks

 

Alternator brushes are done. Either rebuild or replace it.