I have a 2004 Vibe, and the AC Light comes on and the engine sounds different but, the Clutch on the Compressor is not engaging. I was told I need a new condensor because the clutch is part of it and does not come separately.
If your diagnosing an electrical problem, and need to locate components in the electrical system it's best to have a wiring diagram. There are likely many relays in this car so you want to make sure you replace the correct one. Find a diagram here: http://bit.ly/mitchell_repair_manuals_online