Yes, tech1 the drier/hose WAS a problem on 1996-97 cars but this is a 1998 E300DT and that has never been a problem on that year!

TO see if the drier is the problem simply feel the temp of high side, if hose or drier is cool enough to touch then it can restric refrigerant & act like expansion valve!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

My a/c is still acting up intermitantly hot on left side and cool on right.
I checked the charge and it shows overcharge about 55-60 at lbs at idle but I noticed that the aux fan is not working.
I checked the voltage to the connector at the fan and there is 12volts and the fan is nice and free but does not run.
Is there some other sensor between the connector and the fan motor? it doesn't look like it.
Could this have been my problem all along even though the charge made it work better? Should I evacuate some charge and replace the fan with a new one? Has anyone replaced one before on the w210? I would appreciate some help, M.B. Doc what do you think?

Thanks

Your A/C system is 7-8 years old! Evacuate the system, replace the drier & then recharge with the correct WEIGHT of R134a refrig!

Then you will know that the system is correctly charged!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

M.B.Doc.
Thanks again, I think that I am going to replace the aux fan assy and then monitor how the system cools. If it cools OK I am going to leave it alone, every benz I've owned so far had a/c problems.
My only other concern is the elevated pressure on the low side, do you know what the operating pressures should be under a given ambient temperature condition? I have the Mitchell repair manual on CD's but it doesn't give much info on A/C.
I have a feeling that I may have overcharged the system with the 12 oz can that I added.
Regards,
Acerejo

Heat blows out of left side when AC should be on. OK, I have recently fixed a problem that appears to quite common from what I have read in posts on this message board, but not too many threads seem to have a full and complete diagnosis detailed, though I must say there were definitely some very helpful posts that lead me to the final fix. To make a long story short, I had a problem with both my evaporator temperature sensor as well as with my duo valve. The actual main problem was the duo valve (it was sticking). I have read many threads that said a common problem of heat blowing out the drivers side while AC should be on might be attributed to the freon charge being low, but I did not find any valid proof of that. In any case, here is how to diagnose and then fix what is wrong.

1) First thing in the morning preferably with the car sitting in the garage turn the key to the on position without starting it.
2) With your climate control on press and hold the “rest” button until the display changes (the left number should come up as “1”, the right number will be value for inside cabin temperature
3) Press the left “auto” button to toggle up through values and the right “auto” button to toggle back down the following are the values that are important to you and first thing in the morning they should all be within a degree or two. If not, then you have a bad sensor – (I had to replace my evaporator sensor which is under the dash in the duct toward the center on the driver’s side. Buy a new one and then you will know what to look for under there.)
1) Cabin Temperature
2) Outside Temperature
3) Left Heater Core Temperature
4) Right Heater Core Temperature
5) Evaporator Temperature
4) Once the car is all warmed up and you experience the problem where you are blowing heat out on one side (or possibly even both) while calling for AC, go to the above mentioned diagnostic display while the car is running and look at the heater core temperatures. When running full AC they should be somewhere in the 60’s or even lower. If you are having a heat on one side issue, you should see this right away by noticing a big difference between value 3 and value 4. The hot side might be up between 150 and 200.
5) With the AC still adjusted to “low”, open the hood and tap the duo valve with something metallic and see if that “Stuck high heater core temperature” drops. If it does, your duo valve is still trying to do what it is supposed to and is just sticking. If not, You may need to simply replace your duo valve and or test it electrically which is a whole other story (there are other threads in here that can help the ultimate do it yourselfer rewire one of these, but I think it is way too much work unless your are a skilled electrical circuits guy.)
6) If tapping your duo valve gets your AC blowing, let the engine completely cool, remove the three torx head bolts (remove the entire duo valve if you really want to do it right though it’s a bit of a pain to get off) and carefully slide it up. Pay close attention to the small parts that com e out and be careful not to drop any. Also be very careful not to crack or break the rubber gasket below the unit or you will have to replace it somehow and I am not sure how easy it is to get that gasket. I reused mine, so hopefully you can also reuse yours.
7) Once apart, you will notice the cone shaped pieces, this is what is sticking even though it does not look like there are any rough spots anywhere (at least mine did not). I cleaned these very carefully with a dremel tool wire brush attachment. Clean off any debris anywhere and be very careful not to damage the seats that these cones fit into.
8) Reassemble the duo valve warm the car up fully and be sure there are no leaks around the valve – That’s it – stick duo valve.
I cleaned mine about six weeks ago and the climate control has been working flawlessly after struggling for about a year or more. When I found through the diagnostics that it was definitely the duo valve, I was going to change it out, but found that it was over $200, so that is when I decided to take mine apart. Only took me about an hour to do the entire job – well worth the try.

Leszek,
Thanks for the information, I will try to follow it this weekend as I still have the problem.
Acerejo

If the duovalve is working and the refridgerant charge is low, you will get ambient air out of the left vents and very cold air out of the right vents. My car was doing just this. As the high-side pressure rose due to load, the left-side air decreased in temperature. Adding a bit of refridgerant seems to have solved the problem, although I will be looking at the receiver/dryer and hose in the future for my '96.