COMPLEX: Audi A4 2006. Pic. Unknown.
COMPLEX: Audi A4 2006. Pic. Unknown.

I OWN an Audi A4 2006 model. The car has clocked 144000km. I have not used it for the past three weeks because of an engine problem.

I got advice from an experienced mechanic, who informed me that the aircon pump was damaged.

I contacted the Audi agents in Vereeniging and was given a quotation of about R13000, excluding VAT, for a new pump.

Since I cannot afford this I would like to find out what causes the aircon pump to be damaged.

And why is the aircon pump so expensive? Where can I get it cheaper? Is it advisable to buy a second-hand pump and should I, in view of the problem, take my car to a private mechanic ?


(by email)

The aircon pump (or compressor) can be damaged in two ways.

Firstly, the bearing on the drive pulley can pack up, perhaps because of misalignment of the drive belt or because the belt has been too tight, or just through normal wear, possibly accelerated by dust or water getting into the bearing.

Secondly, the pump can suffer an internal seizure of the little pistons doing the pumping action.

This is usually caused by insufficient lubrication, owing to some of the gas having leaked out, taking lubricating oil with it.

People often make the mistake of leaving the aircon switched off for long periods, especially in winter.

The rubber seals inside then dry out, causing a leak at start-up.

For this reason aircon specialists recommend that drivers switch on their aircon at least twice a week.

The price you were quoted is not unusualfor a new pump.

A compressor is a complex, high-precision assembly, probably imported.

But you have other options. If the compressor has suffered internal damage you can get a remanufactured unit for the Audi at about a quarter of the price of a new one.

For this I suggest you approach a private workshop specialising exclusively in car aircons.

Use the Yellow Pages as a source and phone around until you find one that sounds professional and helpful.

Be aware that replacing an aircon compressor is a lengthy, complicated re-gassing procedure to go through, which will add substantially to the cost.

It is a mystery to me why the car cannot be driven.

If it's an internal seizure of the compressor, the pulley should still be free to turn as long as you don't switch the aircon on. (The pulley is connected to the internal drive gear by a clutch which only engages when you turn the aircon on).

I can therefore only surmise that the pulley bearing has packed up. This will make the pulley difficult or impossible to turn at all times and it can be confirmed by trying to turn the pulley by hand, once the drive belt has been removed.

If you feel resistance, or roughness in the bearing you need a new bearing.

It should cost no more than R1000 to replace a pulley bearing.

But if the compressor has to be removed to do the job, as is often the case on modern cars with cramped engine bays, it will be necessary to go through the re-gassing routine afterwards and that will push up the cost.