Ipod IS75 & WS420 Problem

I just purchased an IS75 to use with my IPod instead of using the head phone to aux input on WS420. My plan was to use the RCA input on back of WS420 and switch them out with the head units RCA’s that are currently plugged in. Problem I get is when the RCA’s from the head unit are not plugged into WS420 and I flip the stereo toggle switch on the dash to turn the system on then there is no power to head unit, ws420 or amps. I guessing that the remote wire is not turning them on which I find strange because the only thing I disconnected was the RCA’s, all power wires are still connected. I would like to have the ability to switch out the RCA’s on WS420 so that I can play a cd with the head unit or use the RCA’s for a good connection to IPod. I know I can probably turn system on with head unit connected then after everything powers on switch out RCA’s but this would be a major pain because I use the IPod 90% of the time. Any suggestions other then rewiring power wires?