remote controlled negative

I am looking to control a motor that needs the ground to complete the circuit. I want it to be remote controlled from at least 300 feet or more. I do not want to change the motor because it runs on a timer also and will do this 10 times once we figure it out. Most units I have found switch the + and carry the - straight thru which would run the motor till the battery dies.

You can use the units that you have found and wire the +12v constant direct to the (+)motor and only use the (+)control unit to control a negitive wired relay. Connect the control unit (+)to the 86 on relay, 87,85 to ground, and 30 to (-) motor lead.