disconnect power to cruise control
 

My 84 300SD has been great so far but I made the mistake of trying to use the cruise control going up the Maine turnpike the other day. It started out ok but soon started hesitating a little. I switched it off without a problem. I was also using the cigarette lighter in the rear door to recharge my cell phone. I later noticed that my instrument cluster was dead, turns out it was a blown fuse. Replace the fuse and it blows as soon as the engine is started. The guages are activated while the glow plug is warming, as soon as I start it they die. The fuse is blown again.
I'm thinking it most likely related to the cruise control and would like to disconnect the power to it to see if that solves the problem. How do I disconnect it?

The cruise amp in the driver side floor panel. Just pull it out. I don't have access to the pic at the moment, but its the biggest metal box down there.

which one
 

I took a look under the dash on the drivers side, lying on my back looking straight up, behind the knee bolster. there are 4 different size boxes lined up beside each other, none stands out as much larger than any other. Which one is it?

Which box is it?
 

My Cruise Control Amps have all been aluminum in color and the connector, rectangular oblong, have attached at the bottom.