No cold air
- Low refrigerant from a leak.
- Compressor not commanded on due to pressure, electrical or HVAC control issue.
- Condenser fan not operating or airflow restriction.
- Blend door fault giving warm air even when evaporator is cold.
A/C diagnosis: pressure, command, airflow and leak path.
Automotive A/C faults need leak-aware testing. Do not treat a low system as an endless top-up. Confirm compressor command, condenser airflow, system pressure behaviour and refrigerant loss before quoting repairs.
ARCtick AU068264ABN 92 694 005 760Leak-aware process
Cold then warm
- Evaporator icing from low charge, airflow restriction or evaporator temp sensor error.
- Compressor clutch air gap or coil heat failure on clutch-type systems.
- High-side pressure rising due to poor condenser airflow.
- TX valve, orifice tube or variable compressor control valve behaviour outside expected range.
High pressure
- Overcharge, air/non-condensables or restricted condenser cooling.
- Fan speed fault, blocked condenser fins or debris between condenser and radiator.
- Restriction after condenser/drier or incorrect refrigerant/oil amount.
Low pressure / poor cooling
- Low refrigerant from leak.
- Compressor not pumping properly.
- Expansion valve/orifice issue.
- Temperature sensor or pressure sensor data stopping compressor command.
Advanced A/C pressure interpretation
| Gauge / data pattern | Likely direction | Confirm with |
|---|---|---|
| Low side low, high side low | Low charge, weak compressor, restricted suction or compressor not stroking. | Recover/measure charge, leak test, compressor command, temp drop across lines. |
| Low side high, high side high | Overcharge, air/non-condensables, poor condenser airflow or fan fault. | Fan command/speed, condenser blockage, correct charge weight, evac/recharge procedure. |
| Low side very low/vacuum, high side high | Restriction at TX valve/orifice/drier or blocked line. | Temperature drop across restriction, frost point, line temp, service history. |
| Pressures near equal with compressor commanded | Compressor not engaging, control valve fault, clutch slip or internal compressor failure. | Compressor command, clutch feed/ground, current draw, scan data, control valve duty. |
| Good pressures but poor vent temp | Airflow, blend door, heater tap, cabin filter or sensor/control issue. | Vent split, evaporator temp, actuator sweep, cabin filter and heater line temp. |
Pressure numbers vary with refrigerant type, ambient temperature, humidity, engine speed and airflow. Use pressure charts and OEM charge weight. Static pressure is not a charge amount.
Air-con diagnostic checklist
- Confirm complaint: no cooling, weak cooling, intermittent, noise, smell, demist issue or one-side-hot.
- Check cabin filter and blower airflow first. Poor airflow can mimic refrigerant faults.
- Record ambient temperature, humidity if available, centre vent temperature and engine speed.
- Check compressor command, clutch/control valve operation, pressure sensor data and fan operation.
- Inspect condenser, hoses, service ports, caps, compressor seal area and visible oil staining.
- Recover and measure charge if loss is suspected. Charge by weight, not by pressure alone.
- Leak-test with appropriate methods: electronic detector, UV dye where suitable, nitrogen pressure test where appropriate and compliant service procedure.
Important refrigerant compliance note
A leaking A/C system should not be repeatedly topped up. Refrigerant handling is regulated and should be performed by a suitably licensed technician. Mobile Motive lists ARCtick Licence AU068264 for automotive A/C work.
Common customer explanations
| Customer says | Likely direction | What to verify |
|---|---|---|
| “It just needs a regas.” | Maybe low refrigerant, but the cause is refrigerant loss. | Leak signs, pressure state, service port caps, condenser damage, charge weight. |
| “It cools at highway speed only.” | Condenser airflow or fan issue. | Fan command, fan speed, condenser blockage, high-side pressure rise. |
| “It clicks on and off.” | Low charge, pressure switch behaviour or clutch/control fault. | Pressure data, compressor command, clutch gap/coil, wiring and relay feed. |
| “One side is hot.” | Blend door/dual-zone HVAC issue or low charge depending layout. | Vent split, actuator movement, evaporator temp, HVAC module scan. |