A solution to these problems could be a number of things. Are you hooking up an aftermarket radio to a factory system that has an amp(s)? Jombi:it sounds like you have a short somewhere in your systems rear speaker wiring. Trace that wiring down and rewire if necessary. Cheyner: do you have an external amp in your system or are you using the internal one in the radio? If your speakers are connected to the radios speaker outputs then you'd be powering them off the internal amp. By saying you hooked the radio up with rca cables would mean that you are sending a preamp signal to an outboard amplifier. The speakers would then have to be wired to the speaker outputs of the external amp to get sound. Make sure you're using preamp outputs designed for the purpose at hand: Are you wanting fullrange sound or are you trying to power a sub? Check to make sure you're using the correct set of preamp outputs and check your radios menu to verify that they are turned on. Check your fader settings too and stay sane!