HVACopedia

All brands · Electrical troubleshooting

Motor overheats / trips overload

What is going on

Possible causes and checks for: motor overheats / trips overload.

Likely causes

  • Current overload (excess mechanical load, shorted winding, low voltage, bad run capacitor, start winding stuck in circuit, single-phasing)
  • Overheating without high current (low refrigerant flow cooling a hermetic motor, short-cycle restarts, restricted airflow/dirt, high ambient, high head pressure, friction/worn bearings)

Check in this order

  1. Clamp amps vs nameplate FLA (DC motors need in-line meter)
  2. Voltage at terminals within ±10% / ≥90%
  3. Test run cap
  4. Frame temp + 20°F vs limit (≤72°F over ambient, ~150°F max)
  5. Clean the motor
  6. Check relay/centrifugal switch drops start winding
  7. Ohm windings
  8. Three-phase all three legs present and winding resistances equal

More electrical 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.