Have you tried placing the RCAs in different locations/channels yet?Man..I know it blows, but I myself would prob strat all over with the hu back to the amp,and check all speakers polarity ect.wiring ect.Reinstall so to speak.Try swapping the rt and left rcas..See if the right does the same in the left channel.If so, Id start on that right side with pulling the speakers, check ohm load ect.If it sounds fine, then its a good possibility your RCAs aren't any good/making a bad connection if any, or Pinched somewhere in line.Happened to me before due to fold down rear seats pinched rca,Ok thanks. One thing I forgot to mention is I noticed , when I plugged in that rear right rca jack and the speakers cut off I didn't see the protection mode light go on but the speakers still cut off. That happened 2 or 3 times. Thats the only time I noticed the light not going on , usually that protection mode light illuminates.