A/C system blowing hot and cold in W210
 

Okay, so the W210 is getting kind of weird...

Driver's side vents blow very warm to hot air.... (temp set at 60F on Aircon)
Center vents blow nice cold air....
Passenger's side vents blow lukewarm to warm air... (temp set at 60F on Aircon)

I did a search, there was one hint that a low refrigerent level would cause this, but that was a theory....

The Volvo used to make a clicking sound all the time when it's refrigerent level was low, that was a safety switch clicking off and on the compressor so that it would not burn itself out from the lack of refrigerent.....

So far I do not hear this from the Benz....... Maybe a different design... but only 2 years apart... (1997 Volvo & 1999 MB)

I am really hoping that it is just low refrigerent... but that seems like too easy of a fix... it probably is something to do with the vent actuators or something right?

Yeah, this is going to suck.......

Any ideas? Should I get the system charge level checked? That seems like a good first step... What should it be charged to? (Give me a range!)

You couldn't pick two more dissimilar systems. In the Volvo case the switch you refer to is only protecting the system in its least important feature. The design feature you had experience with uses the fact that the temp of refrigerant is exactly proportional to the pressure when everything works right. So when the accumulator gets cold the pressure goes down and the system is cycled. In your type failure the lack of refrigerant causes the low side pressure to reach cut out when little cooling is actually taking place. Then most immediately the real system pressure returns and the compressor comes back on.

The MB uses a much more sophisticated system. It doesn't cycle the compressor. It uses a POA type device (POA being a shorter version of the POA STV: pilot operated absolute suction throttling valve) to alter the displacement of the compressor and keep the low side pressure from reaching too low. The pressure switches are totally informative and precautionary in the MB system. Thye aren't involved in the refrigeration process.

The 210 car does have a weird change of temp from the ducts with low charge or any reduced refrigeration problem. It usually winds up with the drivers side warm and the passengers side and maybe the center cold. I have had the dual heater valve cause the outsdie ducts to be warm.

Okay, so you recommend checking the charge of the system... it seems like that is the problem...

Thank you!

Yeah... so the system is well filled with refrige.....

So maybe the dual heater valve?

I read the all data thing... 7.3 hours of labor... oh god.... :(