How to fix a parasitic battery leak… 2002 e350 diesel van

Okay, you know you have something that's draining the battery, but don't know what it is. There are a couple of ways to figure this out that I can think of off the top of my head.

First off, you'll want an ammeter to measure the current flowing to the battery. Disconnect either the positive or negative battery cable and put an ammeter between the battery terminal and the cable. Note that most ammeters aren't capable of handling massive starter currents, so don't try to start the van with the ammeter in the line.

Now you should see the current flow that's draining the battery. The object now is to pull fuses one at a time until you see the current flow drop to a reasonable level. It probably won't ever go completely to zero, but there should be very little draw. Once you've found the fuse where the current is flowing, us a wiring diagram to determine what that fuse controls and where the power is being drawn.

Alternatively, you can pull the fuses one at a time and plug in the ammeter probes on each leg of the fuse to check for current flowing when the car is turned off. Same result, but much more fussing with the probes so I'd do it the first way myself.

If you can figure out which fuse cuts the current flow, come on back and tell us and we'll help you figure out what's using it up.