Air Conditioner Won't Start — compressor

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   Use only the thermostat's ordinary controls to confirm its display, cooling mode, and request for a temperature below the room temperature; do not remove the thermostat cover or touch its wiring.

   Expected result: Record blank display, incorrect mode, no cooling request, a valid cooling request with no indoor response, or a valid request where the indoor blower runs but the outdoor unit does not.

   Next step: Correct only an ordinary user setting or battery step allowed by the thermostat instructions, then observe one normal call; arrange HVAC service if the request remains valid but the system does not start.

   Stop if: Do not bridge terminals, open the thermostat, or continue if it is wet, hot, scorched, or smells burned.

   Why this matters

   Why: A thermostat state can prevent a start request. A valid call with no compressor response shifts attention to a safety, control, supply, capacitor, contactor, motor, compressor, or refrigerant condition.

2. Check 2

   Inspect the accessible air filter according to the equipment instructions without opening the air handler, coil, or electrical compartment.

   Expected result: Record clean, gray or blocked, wet, collapsed, incorrectly seated, or inaccessible, and note any weak register airflow.

   Next step: Replace only an accessible filter with the exact type and direction specified; keep the system off and arrange HVAC service if ice, poor airflow, or no-start remains.

   Stop if: Do not reach past guards, clean internal coils, or continue if there is ice, water near electrical parts, smoke, odor, or exposed wiring.

   Why this matters

   Why: A blocked filter can restrict airflow and contribute to freezing or overheating, but it cannot prove a compressor failure. A wet or damaged filter may indicate another system issue.

3. Check 3

   After one normal thermostat cooling request, observe from a safe distance whether the indoor blower, outdoor fan, and compressor area respond; do not remove a grille, disconnect, or service cover.

   Expected result: Record indoor blower only, outdoor fan only, a click or hum without rotation, complete silence, short cycling, or unusual vibration or noise.

   Next step: Keep the system off after an abnormal response and provide the sequence to a licensed HVAC technician rather than repeating the call.

   Stop if: Do not touch the fan, insert tools through a grille, open the unit, test voltage, or try to turn the compressor or fan by hand.

   Why this matters

   Why: Indoor-only operation can indicate an outdoor control, capacitor, contactor, motor, compressor, or safety issue. A hum without start is only a symptom pattern; complete silence can reflect a control or supply interruption.

4. Check 4

   From a safe distance, look only for visible ice on tubing or the indoor coil area, water around the air handler, scorch marks, or damaged insulation; do not touch tubing or electrical components.

   Expected result: Record no abnormality, ice, water, scorching, unusual odor, or a unit that had been running continuously without cooling.

   Next step: Use the thermostat's normal control to stop cooling if ice or abnormal operation is visible, keep the system off, and arrange HVAC service.

   Stop if: Do not chip ice, cut tubing, handle refrigerant, wipe water from electrical parts, or restart to see whether the symptom returns.

   Why this matters

   Why: Ice may reflect restricted airflow or low refrigerant and continued operation can stress the compressor. Water may indicate thawing or drainage problems; scorching or odor raises an electrical safety concern.

5. Check 5

   Without approaching electrical equipment, record whether the system stopped after a visible protection event, outage, or safety indication; do not operate a breaker, disconnect, or fuse as a test.

   Expected result: Record when the system stopped, whether both indoor and outdoor sections changed, whether protection appears tripped from a safe existing view, and whether power is flickering.

   Next step: Leave the air conditioner off and give the event sequence to an HVAC technician or electrician; do not restore power from an enclosure.

   Stop if: Do not reset repeatedly, hold protection on, replace a fuse, open a panel, or continue after heat, odor, smoke, arcing, or water.

   Why this matters

   Why: A protection event can follow an overload, short, water backup, capacitor, compressor, motor, or other fault. A trip that recurs is an unresolved fault, not permission for more resets.

6. Check 6

   Prepare a service handoff with thermostat state, filter condition, indoor and outdoor response, sound, ice or water, and protection history; do not open the condenser to identify the compressor or capacitor.

   Expected result: Record exterior model information if already visible, the last normal operation, and whether the symptom is silence, humming, short cycling, or compressor no-start.

   Next step: Keep the system off for abnormal symptoms and arrange licensed HVAC diagnosis; provide the record and exterior model information to the technician.

   Stop if: Do not touch or discharge a capacitor, test voltage or capacitance, handle refrigerant, remove covers, or repeatedly restart the unit.

   Why this matters

   Why: The record helps HVAC service distinguish a control request, airflow issue, safety lockout, capacitor or contactor symptom, compressor condition, wiring fault, or refrigerant issue without exposing you to stored charge or high voltage.