How to Diagnose the Green LED of the 251 Keypad on 3012 Panel

Issue

Why is the green LED not lit on the 251 keypad?

Solution

The green LED monitors loop status, power supply, and the fuse on the panel. If the LED is shut off check all of the above. Note: zones are supervised with a 1K ohm resistor and 16.5VAC 20 VA transformer is used for AC power.