My '94 rx7 has been having this problem since I bought the car. If the volume on the radio is too high it will turn off then turn back on, or if I have the volume almost too high then hit the brakes at speed it will do the same. The head unit is a Sony Xplod 52x4 that was installed by the previous owner, all the wiring looks well done and correct and the fuse for the radio is the right amp. I have since installed new speakers and a sub, neither of which have any effect on the problem. No other electrical problems to speak of with the car. Any ideas what this might be? Thanks.

 

I pulled the head unit out of the dash and turns out the ground wire had disconnected. I reattached the ground and now the radio works great.