So my friend drives an old, second-hand car in which the original radio has been replaced by the previous owner for an aftermarket radio.
His issue with the radio is that the volume slowly decreases while driving and after about five minutes driving there's no sound coming from the speakers at all. The radio works perfectly fine and when you turn the volumeknob you can see the volumenumber on the display changing, but there's no sound. Turning the radio off and on also doesn't change anything.
I'm guessing it's a wiring issue, but than I'd expect the sound to start/stop immediately while driving when the wires (dis)connect for a moment. Any idea what might be the cause?
(sorry for the late response, I almost forgot about this question :S )
So a couple of weeks ago we swapped the "broken" radio unit with an old one I still had lying around. He has been driving with it since than and hasn't noticed any issues yet.
The slowly decreasing volume is probably caused by an overheating amplifier, as HandyHowie already mentioned. That's all I actually wanted to know as it seemed odd to me and I couldn't find any information about it.
It's either a dying unit or a wiring issue, but for now it works. I'll update this post if the problem occurs again.
Thanks for the help.