Greetings, I'm having an A/C problem with my '99 E300TD just in time for the heat of summer. Any help would be much appreciated! When I turned the A/C on one afternoon I noticed that only the passenger side vents were blowing cold air and the driver side vents were blowing warm air or ambient temperature air. The force of the air flow is equal on both sides just the temperature difference. I've worked the temp controls every which way in hopes it would kick in without any luck. Thanks in advance for your response, it's going to be in the mid 90's in a couple of days, Whew!

 

Since it is dealing with an air-codistributioninstead of heat, I am guessing a problem with the flaps that route airflow in the ducting. I hope I am wrong because these are vacuum contolled and they often have to remove the dash at $$ to repair this.

 

Thanks xvvvz, I hope that is not the case, but your diagnosis sounds highly probable... Does anyone know a way to test whether the flap that is activated when the A/C is engaged is malfunctioning on the driver's side without pulling the dash? Or a way to force it open in case it's just stuck from some deposits? Additionally, is there a temp sensor that just controls the flap on that side that may have gone bad, and if so is it easily accessible? I'd like to exhaust all options before I enter into a cash hemorrage situation$.

 

Most likely you have a leak in the evaporator area behind the dash.

1- Check the presure on the system.
2- if leak is the suspect, then charge the system with gas that has a die.
3- Drive with AC on for a day and look for the sings (die color) of leak to pinpoint where the leak is and verify the leak.
4- Be prepared to spend a few thousand dollars for the repair which is mostly labor. It is recommended to change the part behind the dash that are prone to failure for the age of your car such as heater core and heat sensors, etc.

 

I signed onto Alldata for the 300TD 1999 and seems like the pneumatic flapper valves which are under the dash. Not sure if you'll get my email which I just sent so am responding here also. Maybe we can think and do this thru ourselves (in spite of the valves being under the dash which is not something I really want to do) and save ourselves a bundle. Hope to hear more. I'm not a mechanic but just did a/c system on Yukon -- which is way simple by comparison -- with what little I've heard and seen so far. I'm still game as the valves are pretty inexpensive. I just hate when things don't work. Just bought this one and is good otherwise.

 

In reply to all, I have not had the time to fix this yet, but have done some more research and found what I believe to be the problem while reading another forum (search "duovalve" at benzworld.org or http://www.benzworld.org/forums/w210...light=duovalve). There are numerous posts with the exact symptoms that I have experienced and great info on how to clean a stuck duovalve which seems to be a very common cause for this type of A/C failure. By the way, the passenger side stopped blowing cold air later the same day as my original post. According to all the posts I read, it's a 15min job, just be careful not to drop the tiny torx screws or break the little copper wires when you pop the top on this little engineering marvel. Keep your fingers crossed and I'll post my results as soon as I've tried it, maybe this evening...?!!





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Good news, I cleaned and lubed the duovalve and I'm finally getting cold air on both sides! I also topped up with Arctic Freeze R134+, just for good measure. Hope this fix holds out, but so far so good...