What is it?
 

I have an 85 Dodge W100 4 wheel drive with the 318. There is a grey electrical box on the driver side fenderwell with a three wire plug in it. It's clearly bad as it has black tar substance leaked out of the back of it but I can't find anything on what it is or does. Please help. Not sure if I'm posting this in the right forum or not sorry if incorrect.

If it helps
 

https://cimg9.ibsrv.net/gimg/moparfo...e005ad9170.jpg
https://cimg0.ibsrv.net/gimg/moparfo...5c8abce3a0.jpg
If it helps here are some pics of it

probably some type of seat belt buzzer

The number I was able to make out in the picture is 4111481.

Which google gives back as an "EGR time delay switch". So some kind of emissions deal.

https://cimg5.ibsrv.net/gimg/moparfo...e38c2e5fbb.jpg

You might check this out:

http://www.dodgetalk.com/forums/showthread.php?t=167673

Perhaps your truck also had a run away charging system at some point hence why the the epoxy on your switch is cooked?

Anyway, you'll probably want to replace it unless you plan on removing the emissions stuff from your truck at some point.

That would be correct. Works the Solenoid for the vacuum from the air amplifier on the passenger valve cover.