Forgot to mention when you remove the screw you may get tamper alarm, so when you've reset the reed,you will have to reset the panel if it's a new PA with tamper.
Probably not as the 800L is quite old panel now so the PA used is probably old type with no tamper circuit,
Just thought I would warn you to the possibility of a tamper and the need to reset the panel.
Also a please or thankyou would of been nice.
e manno, December 2012