A/C compressor not working - how-to guide

Many drivers are familiar with the situation when, on a hot day, you press the “A/C” button and only warm air blows from the vents. Often, the reason is that the air conditioner compressor is not turning on. Without it, the system simply cannot cool the air in the passenger compartment. Let's look at the main reasons why this happens.

The main causes of car air conditioner malfunctions

• Low or high refrigerant pressure (due to a leak or clogged system).
• Faulty compressor switch or coil.
• Electrical problems: fuses, plugs, damaged wires.
• Failure of pressure, temperature, or overheating sensors.
• Failure of the air conditioner compressor or its jamming.
• Failure of the radiator fan, leading to an emergency shutdown of the system.

Malfunctions in the electrical part of the air conditioning system

• Relay and compressor coil. The relay is responsible for supplying power to the compressor's electromagnetic clutch. If it sticks or the contacts are burnt out, the compressor will simply not receive power.
• Coil (electromagnetic clutch). It pulls in the compressor disc, connecting it to the pulley. If the coil is burnt out, the compressor will not engage and will not start compressing the refrigerant.
• Problems with plugs and wiring. Due to moisture, salt reagents, or aging, plugs can oxidize. Wires also often rub in places where they bend.
• Blown fuses or a weak relay in the fuse block. This is a simple but common case.

Refrigerant pressure issues in the system

• Low pressure. The most common cause is a refrigerant leak. The pressure sensor “sees” that there is not enough gas and does not send a command to turn on the compressor so that it does not run “dry.”
• Too high pressure. If the system is clogged or overheated due to a faulty radiator fan, the pressure exceeds the norm and the sensor also blocks the compressor from starting.
• Faulty pressure sensor. Even if the pressure is normal, but the sensor itself is faulty, the system “thinks” that there is a danger and does not allow the compressor to start.

Mechanical causes: compressor, fan, and radiator

• Air conditioner compressor failure. If it is jammed or the valves are damaged, the compressor will not be able to start, or the clutch will fail due to overheating.
• Faulty radiator fan. When the air conditioner is turned on, an additional fan always starts (or the speed of the main fan increases) to cool the condenser. If this does not happen, the pressure in the system rises sharply and the compressor shuts down due to a high pressure emergency shutdown.
• Dirty condenser (air conditioner radiator). Dust, insects, and lint significantly reduce heat exchange, the pressure in the system rises, and the compressor stops turning on.

How to quickly diagnose a car air conditioner yourself

Before going to a service station, you can perform a few simple checks to get an idea of what the problem might be.

• Check the fuses and relays. Carefully inspect the fuse box under the hood, find the one responsible for the A/C, and make sure it has not blown.
• Inspect the plugs and wiring on the compressor. Sometimes the wires from the clutch simply break off or the plug falls off.
• Turn on the air conditioner and see if the radiator fan is working. If not, the problem may be with the fan, which is preventing the compressor from turning on.
• Listen for the compressor clutch clicking. When you turn on the air conditioner, you should hear a distinctive clicking sound as the electromagnetic clutch engages. If you don't hear it, the problem is most likely with the electrical system, the relay, or the coil.
• Check if the air conditioning pipes are cold. If the compressor has turned on but the air in the cabin is not cold, the system may simply be low on refrigerant.
• Pay attention to the indicators on the dashboard. In many cars, if the system detects an error (for example, the sensor detects too low pressure), the A/C button may flash or go out immediately after being pressed.

When to call a specialist and why choose STS

If, after checking it yourself, the air conditioner still does not turn on and the air conditioner compressor does not start, you should contact a specialist. A car air conditioning system is more complex than it seems at first glance:

• pressure gauges are needed to measure pressure;
• special scanners are needed to read sensor errors;
• UV lamps to find refrigerant leaks.

STS specializes in repairing and servicing car air conditioners and offers:

1. Comprehensive diagnostics of the air conditioning system, including checking the refrigerant pressure, compressor condition, fan operation, sensors, relays, and coils.
2. Professional refrigerant refill with weight and pressure control to keep your compressor running smoothly.
3. Leak detection and repair, replacement of seals, hoses, and gaskets.
4. Repair or replacement of the compressor solenoid valve and restoration of electrical wiring.
5. Warranty on all work and spare parts so you can be confident in the result.

A car air conditioner is not only about comfort, but also your safety in hot weather. If the air conditioner does not turn on, the fan does not spin, or the compressor does not start, do not put off fixing the problem. Contact the professionals at STS, who will quickly diagnose and repair the system so that your car will once again have a pleasant, cool climate even on the hottest days.