Radio no sound and/or cracks

Hey, for a few days now I’ve had a crack on the speakers or sometimes even no sound at all. I’ve tried a lot. I’ve changed the radio and wobbled on all kinds of cables, etc. – nothing. The only thing I can do to cause the error myself is to set the air conditioning so cold it goes and wait 2-3min. First it starts to crack, shortly after that there’s no sound. When I turn on the heater afterwards, it takes 2-3min until it starts to crack and shortly after that I have no problems. Does someone happen to have the same problem or can someone tell me what’s sitting between the radio and the speakers? Or whether the radio is directly connected to the speakers? If there’s something there, you just get there? Or does the entire dashboard have to be removed? MfG