HVACopedia

All brands · Refrigeration troubleshooting

Won't start, hums or trips overload

What is going on

Possible causes and checks for: won't start, hums or trips overload.

Likely causes

  • Open start winding or start relay (no pause at combined start+run wattage)
  • Failed start/run capacitor
  • Current relay not level/stuck
  • Potential relay wrong rating
  • PTC relay not cooled (2–5 min)
  • Starting against unequalized pressures with PSC/split-phase motor
  • Stuck rotor (long idle, plating, liquid refrigerant)
  • Low voltage

Check in this order

  1. Wattmeter start signature (B84)
  2. Discharge + test caps (ohm swing test and µF)
  3. Check relay per C8/C9
  4. Verify voltage
  5. Ohm C–R, C–S, R–S vs table A23
  6. Megger to ground
  7. If all electrical tests pass → hard start kit (B95)

More refrigeration 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.