2005 F250 HD extended cab 6.0 diesel

I have a short somewhere that is draining the battery. If I drive the truck every day, no problem but if it sits for about 3-days, the battery goes dead. Batteries are fairly new and good.

Disconnected the batteries and put a test light between the negative cable and the negative negative pole on battery to monitor power draw when key is off.

What draws power is the #2 cluster, the radio (clock), alarm system (after market), and the security module. If I pull the these fuses, there is no detectable power draw. I can turn the key on, turn to start position, etc., and when I return to off, the test light turns off. No power draw. Good (I thought). So I ledt these fuses out, reconnected the battery, and drove the car a day or so with no problem (except no radio, no 4x4, etc).

Left the truck sit and 3-days later, the battery is dead again.

How else is there to detect an electrical short or what could be drawing power ?

Thanx for any thoughts

 

Start be disconnecting just the alarm system to see if the draw goes away. You need to try and narrow down which device is causing the draw.

 

borrow a meter.... a multi-meter with a 10 amp current reading..

test light has little value for this type of problem..

also have both batteries "" LOAD "" tested.. at an auto parts store ( most do it free )...
as its possible to have an internal short in battery..