Air Conditioner: Low head pressure, starved evaporator, high superheat and high subcooling readings, short cycling, poor cooling in winter
Low head pressure, starved evaporator, high superheat and high subcooling readings, short cycling, poor cooling in winter on a air conditioner: Possible causes and checks for: low head pressure, starved evaporator, high superheat and high subcooling readings, short cycling, poor cooling in winter.
Common causes of low head pressure, starved evaporator, high superheat and high subcooling readings, short cycling, poor cooling in winter
- No/failed head pressure control: louver bellows or linkage stuck
- Fan cycling switch failed
- Fan speed control thermistor bad
- Receiver heater out, ORI/ORD/LAC valve stuck or wrong setting
- Receiver too small to flood condenser
- Insufficient charge for winter flooding
- Split condenser valve not shifting
- Strong cold wind
How to fix low head pressure, starved evaporator, high superheat and high subcooling readings, short cycling, poor cooling in winter: step by step
- Head pressure vs ambient
- Louver movement
- Fan operation vs pressure, ORI setting and ORD ~20 psi differential
- Charge/receiver level (sight glass)
- Split valve position and bleeder line
- Check valves
If the unit shows an error code, look it up: Carrier Air Conditioner codes Goodman Air Conditioner codes KeepRite Air Conditioner codes Lennox Air Conditioner codes Trane Air Conditioner codes
Source: General HVAC service practice — verify per model. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.