a/c switch
 

I recently had satellite radio put in my 96 econoline van. Now when I put my A/C on theres a loud noise from the engine and the engine wants to stall. The same sound happens when i set the heat to defrost. The radio was hardwired to the A/C switch fuse. So we unhooked the radio and now it's still happening. Does this make any sense? How could a simple install cause this problem?