Can I make 3 wires work with a 4 wire system?

Not without changing out all of your room and patio stations.

If you have 4-conductors (wires) servicing your system and you want to change it over from a 4-wire to a 3-wire, you must do the following:

  1.  Change the jumpers on the back of the DMC3-4 master from 4-wire to 3-wire;

  2.  Change out all 4-wire room stations to a DMC3R or DMC3RS and all 4-wire patio stations to a DMC3RW.

  3.  Connect the red, black, and green wires at both master and stations ~ do NOT connect or use the white wire.

Also, please note that the 3-wire configuration can only use up to 13 stations (including room, patio, and wall or ceiling speakers).