loud bass with radio off

In my eclipse i  am running a kenwood 7202 to 2 kicker comp vrs which is hooked up to the stock infiniti radio/headunit via speaker level inputs from my rear 6x9s. I have found that when my radio is off as in no fm or am radio and no cd or tape that a very loud bass humm comes out my subs. it is very loud and seems to dim my lights a fair amount and so i either quickly shut off my amp or switch to cd and it stops. I've only had this happen while my car is not running and have not turned the radio off when it was running not sure if makes a difference. I've also had this amp hooked up before to a different sub and didn't have this problem but now after nothing being in my car over winter and just adding this setup now its started. Anyone know what is causing this?

You will have to install a switch inline with the remote wire of the amp.  Your radio is turning off and the amp is staying on.  When this happens, the rear speakers are allowed to float around with nothing stopping them from moving.  When they move, they produce voltage and send a signal to the Line Out Converter, this sends signal to your amp.  When the amp sees the signal it moves the woofer.  When the woofer moves, it moves the 6x9 and the cycle begins again.  You really have 3 choices, connect converter to the front speakers, install the switch so you can turn the amp off. Or leave the hatch open so the cycle is not so violent