What would cause a matsushita model 86120-04090 car radio to light up change stations but no sound?

Ok Lets see...

First of all, there are some failures that can be produced by a wire that is broken or is not correctly pluged in, but exactly, the damage is located inside the radio. You can see the AUDIO AMPLIFIER INTEGRATED CIRCUIT, this is one of the most recognized failures in radiOS, or can be, also your speakers. Greetings for Costa Rica.

PD:You can send it to a specialized technic in electronics.