I have a 99 f150 with the 4.6l triton v8 the battery keeps dying after 3-5 days after a full charge I replaced the battery and terminals then issue kept on so I replaced the alternator still having the issue I have no clue what’s causing it has anyone had this issue?

 

Parasitic drain or high somewhere? What is staying plugged in or powered on? Look at the aftermarket added on stuff first. Then go over under the hood, undercarriage, behind the dash ... looking for areas in harnesses and wiring grommets that may be rotted, cracked, shorting. (eg high power lighting can easily drain the battery faster than the alternator can charge it)

If you charge the battery, and leave it disconnected from the truck. Does it hold the charge and still good 3- 5 days later? If not, it is the battery that is defective. Note: "new" batteries are not always good. There are duds, rare, but there.

 

So went to get the battery charged since my charger took a crap and the truck wouldn’t jump for some reason tested bad replaced it again. Now the truck still won’t start the battery light is on and the passenger airbag light came on and neither that light nor the battery light turn off when the ignition is off so I disconnected the battery and haven’t had time to mess with it again. The only aftermarket thing in the truck is the radio and I’ve checked those wires