Although there are no longer inspection windows, one can substitute for them for a short time by using an absolutely pressure-safe glass container. With either only one connection to the high pressure (red) or with an additional one (blue) on the low pressure side, one can integrate this into the circulation of the air-con.

This can only be done, if a vacuum is created in the device, i.e., removing the existing air using a suitable pump. This may take a certain amount of time. Once the quick-connection couplings in the vehicle are correctly mounted and with the hand-valve still closed, one should hold the glass cylinder with the blue side pointing upwards.

Now the testing can start. During the test, one must take care that no liquid refrigerant gets into the compressor, which cannot compress this and which will result in serious damage being done. Once the engine is started and the air-con is adjusted to full power, the low pressure side can be opened.

Coolant flows in from the top. Should the system be filled with PAG-air-con oil, in the otherwise clear liquid, a light, yellowish-green coloured film will become visible on the walls of the cylinder. Other oils can, after having had time to settle, float on the top of the coolant. Otherwise, it's a matter of closely checking the coolant, if possible, against a backlight.

You will notice, that the glass container should not be completely filled. Neither should it appear to be dark coloured because this would indicate overheating and possible damage to the compressor. A very bad sign would be, if there are shavings floating around. The presence of water points to too little dryer-capacity, which should then be replaced.

Once the inspection is finished, the coolant should slowly be sucked out from the low pressure side. Finally, there is only the line to the high pressure to be opened. An advantage would be, having an air-con service- device nearby, not only for the evacuation, but also because anything remaining in the glass cylinder and it's tubing, must be removed, cleaned and the contents must be suitably disposed of. 11/14