#4 Fuse blowing in an unusual way?

Fuse #4 goes to the multi-function switch which must be bad, I would remove it for inspection. You may have wiring that is grounded for the circuit so be ready for that which will take some testing, but this guide can help you with that:

https://www.2carpros.com/articles/how-to-check-wiring

I would start with the headlight wiring. I see the anti-theft module is tied into the system which would explain the door opening trigger. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.

Here is an update: I removed the multi-function switch, and tested resistence on the DB/O wire to ground and got 4 millions or so Ohms. I'm new to electrical work, but from my limited knowledge this tells me I have a short to ground somewhere between the connector and the fuse box?

That is like nothing for a short to ground. Does the fuse blow with the switch disconnected? I would check the dome light bulb sockets to make sure there is not a melted connection.

UPDATE #2: I saw that there is another circuit on a T/W wire from fuse #4 (see attached diagram) to the headlight switch. So I disconnected that harness and tested the T/W wire in the harness. It was reading OL on the meter to ground. Went back and tested the DB/O wire on the multi-function switch and now it was reading OL. Looks like it was the headlight switch. To further investigate I tested the pins on the headlight switch according to the test table attached. When I tested across D1 and D2 (with the wheel turned all the way left, in detent) I get resistance that fluctuates between open and closed. Will be ordering a new headlight switch. Thanks.

Good job, I think you found the problem, please let me know.

Okay. I replaced the headlight switch and the multi-function switch (because it had some issues with the intermediate wipers anyways); however, fuse #4 is still blowing when turning on the lights. It doesn't seem to matter if I open the door or not (maybe it was just a coincidence before). What should I do now to find/narrow down the problem?

So, I would check out the bulbs and sockets, these can melt and cause a short, also, does the van have a trailer hitch? if so the trailer wiring is famous for causing this kind of problem so check out the trailer wiring as well.

https://www.2carpros.com/articles/no-tail-lights-exterior-running-lights-tail-lights-out

Please go over this guide and get back to us.

Hi, I have a bit of an update and need some advice. Here is where we are:
1. I'm not measuring resistance from the T/W to ground on the headlight switch anymore (with the fuse pulled out of course).
2. Now, I was getting resistance from the BR wire at the headlight switch to ground.
3. After pulling a large, diagonally situated, black plug against the firewall behind the battery on the driver's side (just below another white colored vertically situated plug), I am not longer seeing resistance on BR to ground at the headlight switch.

So, this tells me that the short somewhere from that big plug onward. Does anyone have a detailed wiring diagram, that shows the connectors and locations involved w/ the BR wire.

Update: I think I have misunderstood the fundamentals of testing for shorts in a circuit. As such, I think I need to learn some more and re-assess. I think this thread has been a bust and can be deleted. I will open an new thread, once I have a better understanding and can formulate my question better. Thanks.

Sounds good, thanks for letting us know, we are here to help, please use 2CarPros anytime.