HVACopedia

All brands · Air conditioner troubleshooting

Won't engage

What is going on

Possible causes and checks for: won't engage.

Check in this order

  1. Outdoor sensor ≤ cut-in (e.g. 65°F)
  2. Indoor needs cooling
  3. Humidity below limit (enthalpy), Y1 energizes damper relay/free-cooling damper
  4. Blower on
  5. Barometric relief damper opens. p.989 [963]

More air conditioner guides

Related

Calculators and reference tables

Take it to the job

All guides, error codes and tips work offline in the HVACopedia app.

Open the app

Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.