[dasting]

The one labeled HEATER relay, far left.

So swap with the one labeled "horn" and see if the horn works. If it does, then the relay isn't the issue. I just had to go through this last week because my AC suddenly stopped working. Relay and fuse both checked out. Both high and low pressure side AC lines were super easy to pinch, so I started filling up the system with refrigerant. Low and behold, I could immediately start hearing a hiss, and located a crack in the condensor, right in the middle, where clearly a rock hit it. FYI - the system has a pressure switch, if the pressure is too low, it will not kick on the compressor (so as not to damage the compressor).

If relay and fuse are both good - start looking for a leak. Chances are if the AC system went from working awesome to not working at all, you have a big leak somewhere.