I believe you have to go into your configuration.h file and tell the firmware which pin you are using for the probe. Using Z-max should be fine, though for my setup I had to inverse the logic of endstop. If you are using the Repetier configuration web tool it should be pretty easy to setup. Not positive about how to go about it in Marlin though, sorry.
You should be able to issue an M119 to see the status of your three endstops and the endstop being used as the probe, though my setup is likely different from yours. They should all read open when nothing is triggered.
Edited 1 time(s). Last edit at 04/08/2015 04:30PM by Kurzaa.