There are problems with the air conditioning. At first glance, one would assume that these are only for experts, such as the question of how we can achieve the most environmentally friendly refrigerant possible. No, such things are also explained in this book, but that is not what is meant here. Rather, it is about the fact that air conditioning can be a cost trap for ordinary drivers.

Quite simply, the person who uses a technically sophisticated and therefore expensive good like a car regularly takes it to an inspection, a better term than 'maintenance', by the way. Why this small but fine distinction? Because maintenance (according to Wikipedia) includes work such as readjusting, lubricating, conserving, refilling, supplementing or replacing.

However, if you look at the 30 actually work-related points of a service plan for a VW Golf, then all but two are checks that rarely require adjustment or refilling. So we'll stick with the term 'inspection', because coming from the Latin origin, it means looking inside.

But there is only now cause for criticism, because although everything possible should be checked by the workshop, the air conditioning is not included. And if you're of the opinion that it doesn't need to be maintained, your only excuse is that you haven't read this book yet.

Anticipating this, we can tell you that an air conditioner contains a gas that only liquefies under considerable pressure. It therefore rushes through some of the lines in a state in which it can also easily pass through hose walls by diffusion and connections. We will substantiate this with figures from a specific measurement.

For example, in a VW Golf with less than 50,000 km, 135 g of 525 g of refrigerant had 'disappeared' after seven years, which accounts for 25 percent. What is almost worse is that 5 ml (18 percent) of the original 28 ml of oil were missing. It is reasonable to assume that this is a comparatively favorable development of an air conditioning system, so it can be much worse for others, especially of course if a defect occurs in the seven years.

No, there was no warning in the display, because no luminaire felt responsible for it. Perhaps you can already guess what, for example, the further loss of oil would do to the compressor, probably the most expensive part of the system. It is even ruined quite unerring because, for example, an automatic air conditioning system (Climatronic) tries to compensate for the loss of refrigerant and thus performance by operating the compressor excessively.

Sure, you could argue that customers are generally recommended to read the operating instructions. But who, as a layman, knows the need for maintenance and the repair risks of an air conditioning system? Asked in the (brand) workshop, they say that all 'filling levels' are checked. Again, in relation to the air conditioning, an almost stupid formulation that is only intended to calm customers down.

You may be surprised, because there are many ways to refill something in the car, the water for cleaning the windscreen, the coolant, even the brake fluid, but you will look in vain for a container with a screw cap for the air conditioning in the engine compartment or anywhere else. This is due to the already mentioned characteristic of the refrigerant to say goodbye to such a container.

At the specialist Hella, we'll take a look at which tests would be possible. The specifies the air conditioning check as the lowest level. If it were carried out as part of the inspection, this could also point to a defect that needs to be repaired quickly. Incidentally, this is recommended every year. The engine should be started and the blower stages should be started through. In the position of the highest possible temperature, you should check whether the magnetic clutch is activated.

With maximum cooling performance and medium fan speed, the temperature at the center nozzle should be 3 to 8°C after several minutes. Then the low and high pressure should be checked with the corresponding target values. To do this, however, a device would have to be connected, as shown above. It is unclear why this is not specified in the operating instructions.

However, this has an advantage for you: You can omit the thing with the magnetic clutch and the low and high pressure and concentrate on checking the center nozzle. Because if the magnetic clutch is not activated or the low and high pressure are not right, you will also notice this in the temperature development at the center nozzle.

So you don't need any tools, nor do you have to open the bonnet. After you've done this a few times, you can certainly make it without a thermometer and repeat the test at even shorter intervals. They would then have made a virtue out of necessity and the purchase of this book would have been worthwhile.