I just stopped by radio shack and the most convenient part I found is a 4-way bridge rectifier ($2.50) which is rated at 25 amps forward current and 50 volts reverse breakdown voltage so there is no way the part will blow out. The bridge rectifier uses slide on lugs so you can put a crimp connector on the wire, i.e. no soldering required which can be difficult on large gauge wire. The bridge has 4 terminals so I will just cut the two unused ones off. It has a mounting screw hole in the middle and the base is not electrically tied to the part.

Like mcduck says you want the cathode terminal on the +wire. The corner with a notch is a cathode so you would connect that terminal to the + clutch wire, and an adjacent terminal would connect to ground (not the diagonal terminal). The part is not spliced into the wire, it is attached in parallel from + clutch wire to ground. If you connect it in reverse it will short your clutch wire to ground and blow a fuse somewhere when you turn the a/c on.

I am going to get mine fixed as soon as the engine cools off. I am glad you brought the topic up.

R Duke