Audio Systems: No sound from speakers, infinite resistance, 4 ohms

Question
My Blaupunkt radio/cassette unit is faulty - it powers up ok (LCD display working), but there is no sound coming from the speakers. When I press the increase volume button, there is a slight 'clicking' noise coming from the speakers. Other than that, nada.

Any ideas?

Answer
remove the stereo, unplug the harness, wire leads to a AA battery. Touch the battery leads across the car's speaker leads (one pair at a time). You should hear a crackle at each speaker. If you have a multimeter, you should have about 4 ohms on each speaker, and infinite resistance to ground or any other speaker lead. If this all checks out the amp in the deck is shot.