The Stovebolt Site Forums The Shop Area The Electrical Bay Another bad alternator?

FIRST: Battery terminals clean. Alternator grounded well. Battery to motor, motor to chassis, chassis to body grounds all checked.

Then:
Use a separate multimeter at the battery posts. Around 12.5-12.6V motor off. 13.5-14.5V high idle and short rev. Report the results of the multimeter. NOT the voltmeter (for now). Probably best to do the tests after driving and again after truck sitting awhile to detect a battery problem.

Aftermarket alternators have been known to be junk. Hope you are getting a good brand and a good warranty. After you buy another battery and alternator you should have the FLAPS check with their handy dandy hand held machine to get a baseline reading of both. When installed and running in your truck.