Volkswagen Golf Mk5 Air Conditioning Compressor Faults

This page covers the air con compressor on the Golf Mk5, built from 2003 to 2008 in petrol and diesel form, and how to tell a compressor fault apart from the simpler causes of warm air. Compressors for other cars sit within our air conditioning repairs.

Why is my Golf Mk5 blowing warm air?

Warm air from the vents means the refrigerant circuit is no longer pulling heat out of the air on its way into the cabin. On a Golf Mk5 there are four broad reasons for that: the system has lost refrigerant, the compressor is not being asked to run, the compressor cannot do its job, or the refrigerant is cold but the air is not reaching you properly. Only the third is a compressor fault, and it is the one this page deals with.

Most Golf Mk5 engines are listed against the Sanden PXE16: the 1.4 and 1.6 petrols, the 2.0 FSI, the 1.6, 1.9 and 2.0 TDI diesels, the 2.0 SDI and the 3.2 V6 all appear on our Sanden PXE16 compressor page. If your engine is not among them, the number on the compressor’s label settles which unit you have.

The PXE16 is a variable-displacement compressor. Instead of being switched fully on and fully off, the amount it pumps is regulated electrically by the car’s climate control. So if you have read advice about listening for a clutch clicking in when the air con is switched on, it may not describe your car. What matters is whether the compressor pumps when it is asked to.

Searching by the number printed on your compressor? Put that number on the repair form exactly as it appears on the label, alongside the engine and registration, and we will match it from there.

What are the signs of a failing Golf Mk5 air con compressor?

A compressor on its way out tends to show one or more of these. Some point at it firmly; others are shared with faults elsewhere in the system.

• Warm or barely cool air. The fan blows normally and the air con is switched on, but the air coming out is no colder than outside.
• The compressor not engaging. The system is switched on and the compressor does not start pumping. On a compressor fitted with a clutch, the clutch does not pull in.
• Noise when the air con is on. Grinding, rumbling or rattling from the front of the engine that changes or stops when the air con is switched off.
• A seized compressor. The compressor will not turn. That can bring a squealing belt, a smell of hot rubber or a damaged auxiliary belt.
• A leak at the compressor. Oily residue on the compressor body or its pipe joints, or a charge that drains away again after the system has been recharged.
• Cooling that comes and goes. Cold air on some journeys and not others, or air that starts cold and then fades.

One symptom alone does not condemn the compressor. Noise and seizure point at it most strongly. Warm air and intermittent cooling can just as easily come from the charge or the controls, which is why the checks further down this page come before any compressor is removed.

Why do Golf Mk5 compressors fail?

A compressor is a hard-working mechanical unit bolted to the engine, and it wears for system-level reasons rather than because of anything an owner did. These are the causes we see.

• Heat cycles. The compressor goes from a cold start to full engine-bay temperature on every drive, and squeezing refrigerant generates heat of its own. Each cycle of heating and cooling adds to the wear.
• Refrigerant loss. The refrigerant does more than cool the cabin: it carries the oil that lubricates the compressor around the circuit. As the charge leaks away, less oil comes back, and the compressor runs short of lubrication, often before the air turns noticeably warm.
• Clutch wear. Where a clutch is fitted, it engages and releases every time the system calls for cooling. Wear builds until it no longer pulls in reliably.
• Contamination. Moisture or debris that gets into the circuit, from a leak that let air in or a failure elsewhere in the system, passes through the compressor on every cycle.
• Age. These effects add up. The youngest Golf Mk5 left the factory in 2008, so any compressor still on the road has years of heat cycles and use behind it.

A compressor that seizes can shed debris into the circuit. That is why, when one has seized, your garage cleans the circuit as part of fitting, whichever compressor goes back on afterwards.

Gas, fuse or compressor: what to rule out first

Several faults outside the compressor produce exactly the same warm air, and some are far quicker to put right. Your garage checks the refrigerant charge and the system pressures first, then works through the rest.

• A low charge, or a leak elsewhere. Refrigerant escaping from a pipe, a joint or another component leaves warm air with a perfectly healthy compressor.
• A pressure-switch cut-out. When the pressures fall outside safe limits, the system protects itself by stopping the compressor from working, so a low charge can look like a compressor that will not engage.
• A blown fuse or a failed relay. Without its electrical supply or control signal, the compressor is never told to pump, however sound it is.
• A cabin blower or air-flap fault. The refrigerant can be properly cold while a blower or flap problem keeps that cold air from reaching the vents, or mixes it with warm air on the way.

If the charge and pressures are right, the supply is sound and the air is being routed properly, attention turns to the compressor. Our guide to common air conditioning problems and solutions goes into these wider faults in more depth.

One pattern deserves a note on the repair form: a recharge that brought the cold back only for a short while. A system that keeps losing its charge has a leak somewhere, and a leak from the compressor itself is one of the faults we repair.

Your own compressor repaired, or a replacement fitted?

There are two routes back to cold air: repair the compressor that came off the car, or fit a different one. The garage work surrounding them is closer than most owners expect. Which route is open depends on the fault: a leak or a clutch that will not engage is repaired, but a compressor that has seized and snapped its shaft cannot be, and needs replacing.

Either way, the refrigerant is recovered before the compressor comes off and the system is recharged once a compressor goes back on. If the old one seized, the circuit is cleaned as part of fitting. A replacement does not remove any of those steps. It changes only which compressor is bolted on at the end.

What a repair changes is what you know about the unit going back in. Ours is your own compressor: its fault confirmed before we began, the repair tested before it left us, and a lifetime warranty on that repair. It is also the compressor already matched to your Golf’s engine, so there is no second part number to check.

How does the postal compressor repair work?

Wherever you are in the UK, the repair follows the same six steps.

1. Fill in the form

   Complete the repair form with your registration, engine, the number from the compressor label, what the air con is doing and whether the system has been holding its charge.

2. Your garage recovers the gas and posts the compressor

   The refrigerant is recovered, the compressor is removed and it is packed securely and posted to our workshop, with a note of the symptoms inside.

3. Fault confirmed on our bench

   We test the compressor when it arrives, so the repair starts from a confirmed fault rather than an assumption.

4. We carry out the repair

   The leak or clutch fault is repaired in our workshop.

5. Checked once more

   The repaired compressor is tested again, and it has to pass before it is released.

6. Returned for refitting

   Your own compressor comes back with a lifetime warranty on the repair. Your garage refits it and recharges the system, as with any compressor change.

Questions Golf Mk5 owners ask about the compressor