I have an E320, 2003 model with 60,000 miles. I just bought it used and this was a noticeable problem. I have no idea how long its been like this. It has a weird A/C problem and I need some help. The Drivers side A/C blows warmer air than the passenger. The A/C compressor is functioning, but the drivers side air blows warmer. I took it to the dealer and here is what they did to troubleshoot (all of this directly from the workorder):

1. Performed short test, no codes related to the problem.
2. Inspected fuses for AC push button unit, all good.
3. Inspected push button unit power supply, all good.
4. Installed known good push button unit, no change.
5. Performed evac of AC System, .25lb low. Charged system with AC Dye. Performed power supply check with meter at compressor wire, all good.
6. While monitoring values of AC compressor, tech noted there was low pressure on the low side 9-15 and very low pressure on the high side 125-150. Need to replace AC Compressor and perform re-check of the system. This is the first step in diagnosing problem...

Again, the air is very cold on all the outlets in the car except the two drivers vents and the RR passenger vent. It's like the left side of the car is warmer and the right is operating normal. To me it seems the compressor either works or not. Why would the compressor cause this problem? Of course the dealer wants $1400 to replace it...

Any help would be greatly appreciated.

Thats correct, the compressor is a single component who has no idea about the left and right side of the car. If you are blowing cold air in any of the vents, the compressor is working fine, unless ofcourse there is a leak somewhere and eventually the compressor will shut down, but that would not be because the compressor is bad.

Is the amount of air coming out from the warm vent the same as what is coming out from the cold vent ?

__________________
Saumil S. Patel

This is a common problem on 210 air conditioners. It is caused by insufficient refrigerant flow in the evaporator.

If the compressor were malfunctioning, I would expect to see a higher reading on the low-side. That seems like a very expensive "first step" to take.

I've seen one example on this forum of a plugged receiver causing this problem, but that was on a '96. I think I also have a plugged receiver in my '96, but I haven't evacuated the system yet.

Insufficient refrigerant, huh !! Makes me wonder if the evaporator coil is physically laid out such that the coil region that form the regrigerant exiting area is responsible for these vents while the coil region that form the regrigerant entry area are responsible for the rest. i.e a split evaporator usage.

If this is the case, then you have superheat when the refrigerant is leaving the evaporator which is more than what it ought to be. One clue of this would be the temperature of the low side hose. Is this hose kind of warm where the low side pressure valve is ?

Then just add some more refrigerant till you get low side pressure around 35. You may just need a little more so that the exiting refrigerant from the evaporator is a little cooler.

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Saumil S. Patel

a case of not enough refrigerant in the system. I am really surprised that the dealer did not do any checks for leaks after putting in the dye. I wouldn't let them touch the compressor until I had taken it to a good independent A/C shop for their recommendation. Oh, by the way, a 2003 car would be a W211 model not a W210 model.

There is a cheap heater valve that MB issued a bulletin on replacement.

I would start there.

__________________
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190E 2.3 16V ITS SCCA race car (sold)
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The air amounts flowing from the air vents are all the same. The blower seems to be working fine at any speed, with and without the "auto" mode engaged.

Currently, there is no indication of a leak. The dealer checked it with the dye...and did not tell me there was a leak. I intend to take it to an independant shop for anaylsis, but I would like more input before taking it. The dealer charged me $200 to troubleshoot it on top of the $500 for the 60,000 mile service. Needless to say, this is the last time I take it to this dealer!

thanks for the suggestions. If you have any more ideas...please advise.

Are the AUX fans running when compressor is engaged? Another possibility is the EVAP Valve. This could be causing poor flow through the evaporator.

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Dennis
2006 E320 CDI Black/Black Leather. Nav, HTD Seats HK stereo 32000 miles.
2000 VW Passat 1.8t 300,000 miles as of Dec 09, 2009 original owner
1997 E300d Silver 300,000 miles As of Jan 05, 2010
3rd owner SOLD

Yes, the Aux fans are running.

Any more ideas?

Thanks

why wouldn't the dealer service rep have known about that service bulletin and matched the problem description with the symptoms and checked the valve? At the minimum, the tech who worked on the A/C unit should have caught that. I would write a stiff letter to the manufacturer about this and name names! These guys charge the highest rates in the business and turn out garbage for their diagnosis.

In the June issue of STARTUNED magazine found at www.mbwholesaleparts.com there is an article on MB HVAC multizone heating systems. I just browsed the article, however, considering your A/C issue you'll probably get some helpful information for when dealing with the dealer etc...

This really pis*** me off. Can anyone give me the SB info on the suspect valve? I want to assure I have the correct information when dealing with this dealership. I told the cashier that I was going to call the service supervisor and complain about the diagnosis. The service rep was useless...

I don't care to pay for "recreational maintenance"...

Have them refer to service bulletin P-B-83.20/72 dated 17 Sept 2004.

Or you could try "squeezing off the heater supply OR return hose(s).

__________________
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

Thank you...

Are these hoses easily accessible? I would prefer to try it myself before calling and complaining.

Is the heater core in this car laid out such that some vents can be cold and some hot ? If yes, and if the valve is not closing properly, then interrupting the heater hose or removing power from the aux water pump should definitely make the situation lot better.

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Saumil S. Patel