Question Re A/C refrigerant pressure
 

When the A/C refrig pressure is displayed on the CC (item 7), on my E320, it reads in range 14-16 bar when car is at IDLE at say a stop light.

Then, when I pull off, the pressure drops to the 6-7 bar range.

Considering the engine and possibly the compressor are now running faster, why does the pressure drop? Just trying to understand what is happening.

Secondary question - On a new car, would there be a similar drop in pressure?

Does your car have a belt driven fan? If so the fan is spinning much faster when moving. Plus you get the airflow over the condenser from the wind. Both of those lower its temp, which lowers the high side pressure.

I'll have to look at that reading in my Passat. It has twin electric fans so their speed isn't dependent on engine speed, and they're very powerful to cool the engine bay during a 1100*F DPF regen.

-J

My E320 also has twin electric fans in front of the condenser. Air flow would also likely make some difference I guess.

But there's no belt fan behind the radiator? From what I have seen the smaller pusher fans don't pull as much air because the fanwheels can't be very thick.