So one day, the battery went dead, overnight. Jumped it, ran the truck, figured it was a bad battery. Autozone put a load tester on it, battery is fine. Next night, it happened again. So I just disconnected the battery when I wasn't using the truck till I got time to troubleshoot it. Well, today I looked at it. Put an ammeter on it with the neg terminal disconnected, showed almost a 7.4A discharge. Pulled the fuses one by one, got to #13 or 14, a 15A fuse, the book calls it the fuse for the "battery saver relay". After pulling the fuse, the load dropped to about 4A. (Still pretty high) where is this mysterious "battery save relay" located? Owners manual doesnt' say. 2002 F150 4WD 4.6 ltr. Any ideas, suggestions?

 

Did you have your door closed and the engine compartment light out when you tested?

 

Remove the heavy lead at the Alternator.
If the load goes down you need to replace the Alternator.
If not you have some other drain.
Remember there are modules that need to time out and remove the hood lamp.
They will all take power until you account for them.
Good luck.

 

Door was closed, so no interior light was on. Even with the fuse pulled for the battery saver relay it showed a 4A draw, I dont think the hood light was on either, i'll check next time. You think removing the alt lead will stop it, indicating a shorted alternator? theing is, the alternator still charges the battery?

 

There is a reason I suggested removing the Alternator charge lead.
The Alternator is an AC generating device that uses Diode rectifiers to change it's output to DC to charge the battery.
A Diode is a 'one way' pass device to current.
If it develops a short or leakage, it will pass current from the battery back to ground discharging the battery but will still charge the battery with the motor running.
There are 3 ways to check for this condition.
1. Remove the lead.
2. Remove the lead, then re-touch back to the terminal. If you see any spark the Diode stack is faulty.
3. A check with an AC voltmeter on it's low AC scale will show the Diode stack leakage as a low AC voltage in the high millivolt range with the engine running.

Yet another way most don't have access to is a Scope check to see the same thing as the AC volt meter check shows.
.
Some times a faulty Regulator will keep the field winding connected after shutdown. This will also show as excessive voltage changes during running such as noticeable head light brightness changes off idle.
.
A warm Alternator case 'after the rest of the engine has cooled' is a sure sign of a back feed drain..

Good luck.

 

 

Thanks for the help, I appreciate it.