Blows fuse after start up. Need wiring Diagram or ez solution.

Go to JD web page, click support, dial in your numbers and read the manual ( you can not download it but can print it out in sections ) find your wiring diagram and check.
JD use either a fuse or a fuseable link.

bulb has water in it

( one question i have is every time the ignition fuse blows do i need to replace the starter relay? ) NO ! You have a dead short to ground on one of the circuits that fuse feeds. Do you know how to find a short circuit ? Video's on youtube show how. The fuse that blows ,is it IGN - A 40 amp. located in the under hood fuse/ relay center ? That fuse feeds B+ voltage to the ignition switch ,which powers up other thing's ,fuse's etc.. Not just the starter relay ! I see five other fuse's that get power from that fuse when ignition switch is in the start or run position . In the I/P fuse panel the gauges fuse #4 10amp , air bag fuse #10 10amp , turn b/u fuse #16 20amp. , Plus trans fuse #20 10 amp ! Pull out these fuse an try to start the van. if the ignition fuse doesn't blow the problem is in one of these other fuse circuits. There is one more fuse that get's B+ power from the ignition switch and ign A fuse ,crank fuse fuse #8 10amp. this powers the control side of the starter relay .
You can find a free wiring diagram here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model and engine . Under system click engine , under subsystem click starting. Click the search button then the blue link.
If you pull those fuse's i mention and it still blows the fuse look for a shorted ignition switch or wiring from ignition to the starter relay , not the relay itself. Park neutral safety switch . Isolate the circuit , pull the relay out of it's socket ,pull the crank fuse #8 in the I/P fuse box. with a ohm meter check to see if that part of the circuit is shorted to ground. Do you know how to do that ? Do you have a volt ohm meter ? You can buy one cheap at parts store .

mercedes service letter:
http://www.aev.com/uploads/file/SPRINTER%20NO%20CRANK%20NO%20START%20.pdf
Replace with 25 amp fuse.

I would try your local Auto Zone. They have everything.

try different fuses starting with lowest then go up but think it is a 30 amp fuse ?

There's a short in the circut. Check continuity of the wires that feed from that fuse (you'll need a wiring diagram to identify each wire). You've got something that is causing too much amperage to move through the circut and the fuse blows. Make sure the amperage on the fuse is correct for the application (your owner's manual or fuse box diagram should tell you what amperage rating to install in each fuse slot).

by looking at the wiring diagram for your truck. the pcm1 fuse only feeds the pcm so most likely it is a grounded wire between the fuse block and pcm. follow the wire harness closely between the two and see if its grounded somewhere. also try disconnecting the pcm and see if the fuse still blows. that would isolate the problem to the wiring. it is highly unlikely that the pcm would cause the problem.

I have wiring diagram. Respond with your email address or fax number and I will sent it to you.