Sporadischer Klimaausfall | Posts 16+

Hello, based on what you're writing, it seems you're having a problem with the refrigerant.

If the fans start running immediately, it usually means there is not enough refrigerant in the system.
The pressure after the compressor is too high for the required cooling capacity. Try to reduce the pressure by cooling it down. -> The blower is running.

If the temperature behind the evaporator is not reached, the compressor will remain running continuously.
This temperature is measured using an NTC sensor. This value determines when the compressor is turned on and off. (NTC_Evap_Out -> Air temperature after the evaporator).
If this NTC sensor is defective, the AC will always cool at its maximum power because the desired temperature behind the evaporator cannot be measured.

Eventually, the evaporator will ice up. This will cause the low pressure in the suction line to the compressor to drop too low. As a result, the anti-icing switch will disengage the compressor clutch. The system will then shut down.

So:

Check the NTC sensor behind the evaporator.
Check the ice sensor.
Possibly check the pressure switch (although it should actually be working correctly).

If you have a manual air conditioning system, it is only activated by the Motronic control unit.
The rule is essentially: if the temperature (T) is greater than the setpoint (T_set), then turn on the compressor; if the temperature is less than the setpoint, turn off the compressor. This information is then sent to the main control unit (MSG).
This regulation can be implemented in a separate control unit, or it can be completely integrated into the main control unit (MSG), depending on the model. This information is then sent to the MSG.




Best regards, Jochen.

Now I'm one step further, thank you very much for the help so far.

I've now read the climate control system data. The deactivation condition is a coolant temperature that is too high. Does this refer to the coolant temperature of the air conditioning system or the engine?
What could be the reason for that?

T2-TDI wrote:

Now I'm one step further, thank you very much for the help so far. I've now read the climate control system data. The deactivation condition is a coolant temperature that is too high. Does this refer to the coolant temperature of the air conditioning system or the engine? What could that be due to?

The engine's fault.
"Read the value using the diagnostic tool. Often, the combination instrument and the engine control unit use two different sensors, so a correct temperature reading on the combination instrument might not be indicative of the actual temperature."

Okay, thank you very much for the good tips!

I've found the error I was having, and perhaps someone else might find this interesting.

So:
I read the climate control data as described, and it indicated that the coolant temperature was too high, which is the shutdown condition. However, after disconnecting all the sensors, and the climate control still shut off during acceleration, I no longer believed that was the actual problem.

'Then it occurred to me that I had read a report in this forum during the winter about 'TDI jerking,' and the best solution was to disconnect the speed signal from the control unit. The jerking then disappeared. Of course, I hadn't checked the air conditioning in the winter, and in the summer, I thought there might be too little coolant. I also didn't see any connection between the two.'