Need Help 12v Diodes???

Figured I'd try you guys on this one.

I've been doing a little rewiring on my pickup. Basically the supercharger has forced me to install some electric fans. I have them set up on a thermostat reading off the "cold" side of the radiator. I would like to trigger the relay with the A/C circuit as well. I pulled a trigger voltage off the pressure switch that will work fine. The only problem is, the trigger voltage from the thermostat will backfeed into the A/C circuit causing the compressor to engage. I figure a diode between the Thermostat circuit, and the A/C circuit will do the trick. The only thing is, I know jack about diodes. I figure the draw will be much less than 1 amp at 12-14.5 volts DC, 15 watts max. What should I ask for at "Radio Shack". One other factor to consider. Being in a truck aome vibration resistance should be helpful. That is if diodes can be affected by vibration.

Any help appreciated...

 

Radio Shack Diodes #276-1144 pkg.of 2

 

I see this fits on a xj , see that silver band on the right , well if 12v is on that side it [12v] no passes to the other side.

any one from the shop will do , get a 10amp one , 50c to a buck....