How to reduce compressor failures
Few components in the air conditioning system are as critical, or as costly, as the compressor. Yet in the aftermarket, compressors are also one of the most commonly returned parts, claims MAHLE, with the company suggesting the problem is that a large proportion of these returns are down to mistakes made during installation – not because of a defective unit.
According to MAHLE, the story is often the same: a new compressor is fitted, but the surrounding system hasn’t been prepared correctly, or vital installation steps have been skipped. The result is premature failure, frustrated customers, and warranty claims that could easily have been avoided.
One in three vehicles produced is equipped with a MAHLE compressor – and the OEM believes that expertise flows into the aftermarket. MAHLE offers a dual-quality programme:
- References ending on P (Premium) are the exact same part as originally fitted by the OEM
- Whereas references ending on S (Standard) provide a more “competitively priced alternative” with the same MAHLE reliability
Best practice counter advice for technicians
If the compressor fails, the entire system is compromised, but dropping in a new unit is not enough – the whole system needs to be ready to accept it. That means flushing away contaminants, checking oil levels, replacing non-reusable components, and ensuring the first start-up is handled carefully. Every one of these tasks is critical, and missing even one can cut short the life of the new compressor.
Take flushing… Whenever a compressor has failed mechanically, swarf and metal abrasion will almost certainly have spread throughout the circuit. Add to that the possibility of sealant residues, degraded rubber particles or even desiccant granules from a saturated dryer, and there is a system full of contaminants waiting to damage the new part.
MAHLE stresses that flushing is not an optional extra; it is the only reliable way to remove these risks. And because some components, like the dryer, accumulator, expansion valve or most modern condensers, cannot be flushed, they must be replaced outright. Skipping this step is one of the quickest routes to another failure.
Oil is another area where oversight is common; MAHLE’s compressors are supplied pre-filled with refrigerant oil, but because the same unit can be specified for multiple vehicle applications, the oil quantity must always be checked and adjusted before installation.
Draining the oil into a clean container, measuring it, and then matching it to the VM’s specification ensures the correct fill. Too much oil, there is a risk of hydraulic lock or reduced cooling performance; too little, the compressor is starved of the lubrication it needs.
Once adjusted, the oil is refilled and the compressor prepared by standing it upright to lubricate the shaft seal, before carefully rotating the pulley to distribute oil evenly. It’s a small but vital detail that can mean the difference between smooth operation and an early failure. To support technicians, MAHLE provides a filling quantity tool, which gives oil specifications for different vehicles: click here.
MAHLE encourages compressors to be installed with new seals at every connection point and insists drive belts must be perfectly aligned. Moisture and air must be fully evacuated before refrigerant is charged, and only the correct refrigerant specified by the VM should be used.
How the system is started for the first time is crucial too: running the engine at idle before engaging the AC and then cycling the system on and off several times allows oil to circulate gradually. Miss this stage, and the compressor can suffer an oil shock that places immediate strain on internal components.
Not a quick fix
Too often, technicians view compressor replacement as a quick part swap, says MAHLE, but, in reality, it is a system-level repair. Without the supporting steps, even the best-quality compressor cannot be expected to last. For MAHLE, this is not just about protecting its reputation, but about giving your workshop customers the tools to protect theirs too. A warranty rejection is bad news for everyone: the factor, workshop and end-customer alike.
