Strange Z-height calibration

[abecker]

While I was tweaking my z-height I noticed when I started calibration that it started at 0 and went to the negatives as I lowed the z height. Then when I set Z=0 and homed the towers, the second time I chose to change Z height it showed the "homed" value for z being above 700. Each time I did this it kept going up. I didn't think much about it until I tried to start a print and the nozzle crashed into the bed. What can I do to get this back to a normal height?

[joe]

Change it in the eeprom. Set it to 300 and redo the z height to set it exactly.