hELLO everyone I hope someone can help. Replaced alternator and battery... car was fine for a couple weeks and then the battery light started to come on. replace negative cable and still the light turns on voltage drops to about 12 V.... light turns off when I rev engine turns back on when idles. turns off when I turn the A/C off and back on when its on. The light also comes on after driving for a bit but has mostly been coming on when im parked....

 

cvrdo: Sounds like the voltage drops when the A/C is on and the RPM is low. Just spit balling, but have you checked the serpentine belt & tensioner?

When the A/C is on, the serpentine belt works doubly hard:
1) The A/C compressor load obviously increases, and
2) The Alternator load also increases to energize the A/C's electromagnet clutch.

To get a sense of how much load the A/C adds to the serpentine belt, consider that when we turn on the A/C, our cars get 1-2 fewer miles per gallon of fuel. The "lost" 1-2 miles per gallon is the extra load on the serpentine belt to power both the A/C compressor and A/C clutch via the alternator.



Again, just spit balling.

 

thanks ill check it out man and get back to you.

 

Welcome to the forum cvrdo,

I've deleted your identical question from General Tech Help and also removed another version from the end of an irrelevant thread. Do NOT post the same question across multiple threads or forums.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham