Saturn Z Axis Microswitch Problem

[Del773]

I've just replaced the screen on my Saturn S.  

After getting the screen working I wanted to check the Z axis was working properly. The red indicator light is on. Moving the Z axis down manually with no build plate fitted, the Z axis moves down to the Microswitch, the machine beeps twice, the indicator light is extinguished and the Z axis carries on down until the microswitch actuating arm hits the base plate where it continues to try and drive down.

Pressing home has exactly the same effect, selecting z=0 has no effect.

What do you think could be wrong?  

Thank you and I look forward to your replies.

[Del773]

After a bit of further research and 'testing' I have solved the problem!

Firstly, the mother board in my printer has 2 identical sockets side by side for the Z microswitch and Mr Murphy and his inevitable law had me plug the cable into the wrong one!  I must pay more attention when I'm taking things apart!

With the plug in the right socket, I turned on the machine, pressed the reset button and hey presto, off it went.