I need so assistance. My 2006 F150 with the 5.4 has a charging issue. If I don't drive the truck every day the battery drains down . I replaced the battery and still does the same thing. I did a system check on the alternator and it is reading 14.40 , so maybe I am wrong but alternator is ok. Any susigestions

 

Could be a bad diode in the alt, it may still charge but it's like leaving the lights on. Battery will drain down over night. It could be another issue though. Dome light, glove box light switch bad and leaving the light on, or even the under hood light. To name a few.

 

Here are a few more! I have seen bad fuel pump relay's stuck on after truck is turned off. Also the ABS pump running too. W/ everything off, listen for anything that may be running.

 

More than 3 weeks in the winter could cause problems. Put a trickle charger on it if not driving for weeks at a time. Will save your battery and alternator from being over work by trying to recharge a half dead battery.(Burning up the Alternator)