no sound, although radio works

@mssteffi start off by checking the speaker output connectors on your radio. Double check to make sure that all connections are properly made. You also want to check under the passenger seat. You will most likely find the power amp located under there. Make sure that it is connected right and all the wiring is intact. Check for any blown fuses in the fuses boxes. If yours is a stock amp check that pin 13 and pin 17 should have 12Volt. Use a voltmeter or similar to check on those. Let us know what you find. remember that a pictures is worth a thousands words. Just in case you have trouble with this, post some images with your question so we can see what you see. Use this guide for that.