I had a similar odd problem. Suddenly no signal (no clicking noise and no indicator on the dash) and no external signal. Odd things were happening with the amp light. As well, the fan stopped working when these other problems appeared.

After much head scratching, if I recall correctly, I followed the wires from the signal unit (the thing that makes the clicking noise). One of the red wires (I think) went to a connection in the back of the dash and other wires ran off that connection as well. Turns out the connector was loose (a threaded stub with a loose nut), and when the car moved a certain way, the wire contacts shifted just enough to cause wierd seemingly unrelated problems. Tightened the nut on the connector and haven't had a problem since.

Anyways, check to make sure the wires are all well joined at the connector points behind the dash. Hope its that simple.

waggin.