Yellow 1 flash Low side fault / low pressure trip / low pressure lockout (older ComfortNet board)

What the control is telling you

Yellow LED 1 flash. Green OFF + red OFF = low side fault (4 protector trips, average run over 3 h). Green ON + red OFF = low pressure switch opened. Green ON + red ON = low pressure lockout. Same meaning as 7-segment codes 01 / L1 on newer boards.

Applies to: Earlier ComfortNet condensers/heat pumps with the PCBHR101-103 or PBBGR101-102 outdoor control (green, yellow and red status LEDs) - ASXC/DSXC/ASZC/DSZC revisions before the PCBHR104 change

Likely causes

• Low refrigerant charge
• Restricted liquid line (drier, kinked line)
• Indoor blower motor failed or not running
• Thermostat set very low

Test and repair steps

1. Warning: Kill power to the outdoor unit before touching wiring, the compressor terminals or the control.
2. Check charge with superheat/subcooling and correct it; leak check if low.
3. Look for a temperature drop across the liquid line drier or any kinks - repair restrictions.
4. Confirm the indoor blower runs at the right speed and filters/coil are clean.
5. Check the thermostat set point.
6. Test the low pressure switch (opens about 21 psig, closes about 50 psig).
7. Low side fault clears after 30 normal cycles; lockout needs a 24 VAC power cycle.

Models that show this code

24 models in Goodman/Amana ComfortNet ASZC/GSZC/DSZC

Other codes on the same units

• EE Outdoor control fault - compressor relay contacts welded
• Yellow 2 flashes High side fault / high pressure trip / high pressure lockout (older ComfortNet board)
• Yellow 3 flashes Short cycling (older ComfortNet board)
• Yellow 4 flashes Locked rotor (older ComfortNet board)
• Yellow 5 flashes Open circuit (older ComfortNet board)
• Yellow 6 flashes Open start circuit / lockout (older ComfortNet board)
• Yellow 7 flashes Open run circuit / lockout (older ComfortNet board)
• Yellow 8 flashes Low or high line voltage (older ComfortNet board)