When i let off the gas and the engine drops to about 900 RPM, the lights go dim for maybe 2 - 3 seconds. The local parts store did a battery check and it is 96%. They checked the charging circuit, and it indicated a problem. I have replaced the alternator, but it is still doing it.
Try replacing the serpentine belt.
Any of these are likely culprits
- replacement alternator is faulty
- alternator pulley is not spinning fast enough, belt slipping etc
- problem w/charging wire between alternator and battery
- problem with charging regulator circuit. If you know how to use a volt meter, batteryshould measure about 12.6 volts before the first start of the day; then immediately after starting engine, 13.5-15.5 volts. What do you measure?