When I turn the key my Arm-A-Door is not arming.

Answer

Possible Causes:

1. There is not any power going to the unit.
2. The unit is not armed.
3. The subassembly is damaged or gone bad

Possible Solutions:

1. Verify there is power to the unit (fresh 9 volt batteries). Try resetting after installing new batteries.
2. Verify the Key cylinder is engaging the microswitch. Verify the microswitch at the key cylinder is good.
3. The subassembly is bad and will need to be replaced.