AC compressor for your car

Fresh air with the air conditioner compressor

The compressor is a central component of an air conditioner, converting the gaseous coolant into a liquid. The subsequent evaporation in the evaporator establishes the desired cooling effect. The compressor also causes a higher fuel consumption when the air conditioner is in operation. Nevertheless, this feature is essential for comfort and safety in a car in summer and in winter.

Compressor function

An air conditioner compressor has a drive part and a compressor part. It is tightly fixed to the engine block. The compressor is generally driven by the V-belt, which is often connected to the generator, servo pump and the water pump. Only rarely the compressor is driven by a timing belt. The risk for the engine is too high and therefore, most manufacturers prefer other solutions. On the compressor side, the component is connected to the cooling system, with its hoses and modules depending on absolute tightness. Therefore an AC compressor should always be of high quality. Otherwise the function of the air conditioner would soon be in danger. The function of this unit is technically very ingenuous: the circular movements of the drive are converted into a linear movement by a swashplate and pistons. The pistons compress the in-flowing coolant tightly, causing it to liquefy. Between drive and swashplate sits a magnetic coupling, switching the air conditioner on and off, so that the fuel consumption only increases when the compressor is switched on.

Defects of a compressor

An AC compressor is lubricated with oil circulating in the cooling circuit. If too little oil is present or it gets lost through leakage, the compressor gradually sustains damage. Moisture in the cooling circuit and particles can clog the compressor. The main cause of a failing compressor is insufficient or unprofessional maintenance, use of the wrong coolant or lubricant or mechanical faults. A defective speed limiter or damaged magnetic coupling can destroy the compressor as well. A deficient cooling performance or noises are an indication of a defective compressor.

Compressor repair

The AC compressor is a complicated component and repair is almost impossible. Its housing is tightly welded and riveted for safety reasons. Disassembly and repair cannot be performed with home tools. The pressure in an air conditioner does not allow for disassembly. Therefore, this component is always replaced. Replacing AC compressor requires draining the coolant and this can only be done in a garage. Installation of the AC compressor is quickly done: it is screwed onto the engine bock and connected to the cooling system with nuts. Nevertheless, filling the air conditioner with oil and coolant is a matter for the garage. It would however be difficult to find a garage unable to perform the entire repair. If this does not concern the restoration of a vintage car, going to the garage is the only sensible option for replacement of an air conditioner compressor.

Prices for new compressors

Amazingly, AC compressors aren't nearly as expensive as you would think. Prices for all brands are relatively constant at ca. 150 EUR (c. £135). The magnetic coupling would set you back another 50 EUR (c. £45). These prices get you branded articles from renowned manufacturers. Nevertheless a compressor, unlike a generator or starter, cannot be replaced with simple tools. The replacement of an AC compressor comes with extensive air conditioner maintenance, including inspection, rinse and cleaning of all other components. Coolant and lubricating oil can only be replaced by professionals. The wrong agents could compromise gaskets and cause the entire system to fail again.