Ok.. To start things out I have a 09 FG2 premium sound system, non navi still installed. I have a mercman bypass harness for my rca's. I followed Hans suggestion on running a ground to the back of my car directly from the battery alongside my power wire (both 4 guage) and using two distribution blocks. and have my rcas ran under the carpet in the middle of the car. I am using amps from a previous install so they were not ideal but saved me alot of money.. I have on RF 2 channel running one infiniti perfect 12.1 sub, and a RF 4 channel amp running my focal access components in the front. I ran into some bad alternator whine at first, so I grounded the amps seperatly with seat belt bolts under the rear seat with some extra 8 gauge wire I had laying around. That almost took care of the whine however i can still hear a slight hum in the sub if i pop the trunk and listen back there. Now that I took care of the whine I also did one part of the big 3 with the last bit of 4 gauge i had and grounded the battery with it. Thinking i was done i took it for a test drive and found out my when i turn my A/C on, even if just the fan, my sub amp turns off, but the other amp is not affected. Any ideas?