The Yorkguard IV and V boards both have diagnostic functionality that will energize the X/L terminal to flash a light at the indoor thermostat if abnormal operating conditions occur.

Unlike the Yorkguard VI, the number of flashing lights on the thermostat will be the same as the diagnostic flash code on the outdoor unit.

The "lockout" can be Reset at the thermostat by: 1) cycling power to the air handler or 2) turning the thermostat system switch "Off" and then back to "On".

LOCKOUT CODES:

Flashes	Description
Heartbeat	Normal operation (No Faults)
2	Hi pressure cut-out open
3	High compressor discharge temperature
4	Low compressor discharge temperature
5	Default defrost (liquid line temp too cold)
6	Discharge (or any) sensor open or shorted
7	Outdoor sensor open or shorted
8	Liquid line sensor open or shorted
9	Bonnet sensor shorted
Fast Flash	Analyzer plugged-in

WHAT TO LOOK FOR:

Flash	Cooling	Heating
2	Bad condenser fan motor Bad cond fan capacitor Dirty outdoor coil Overcharged	Bad indoor fan motor Bad id fan capacitor Dirty indoor coil Overcharged
3	Low refrigerant charge Bad I/D expansion valve Clogged filter drier	Low refrigerant charge Bad O/D exp. valve Clogged filter drier
4	No power to O/D unit Bad compr capacitor Bad compressor Bad contactor Burnt wires to compressor Bad sensor	No power to O/D unit Bad compr capacitor Bad compressor Bad contactor Burnt wires to compr Bad sensor Un-insulated sensor Overcharged
5	N/A	Bad O/D fan motor Bad O/D fan capacitor Low refrigerant charge Bad O/D exp valve Bad sensor
6	Bad sensor Bad wiring Check all 3 sensors	Bad sensor Bad wiring Check all 3 sensors
7	Bad sensor Bad wiring	Bad sensor Bad wiring
8	Bad sensor Bad wiring	Bad sensor Bad wiring
9	Bad sensor Bad wiring	Bad sensor Bad wiring