On my '99 E320, the climate cotrol blows so-so cool on the passenger side, but blows warm on the driver side, when set to LO or 14degree temperature. Which part am I looking at replacing? Thanks a Lot!

Do a search - sounds like your charge may be low...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Your low on refrigerant. You'll need to recharge it and look for leaks.

You have a really modern Mercedes, with selective heat by position in the car!! Perhaps you can sell that system to others?? (Just kidding) BC

__________________
Ben Harrison Carter
1999 Mercedes ML320 87K
1992 Mercedes 300CE 89K
1995 Corvette 29K -- Sold Dec 09
1989 Mercedes 420SEL 99K -- (Sold 4/08)
1968 Mercedes 230S (106K) (Sold 9/06))
1976 Mercedes 450SEL 130K (Just sold - 06)
1961 Mercedes 220Sb (sold years ago)

Wouldn't that be "zoned climate control?"

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Check your heater hot water control valve (duo-valve);solenoid valve which controls the flow to each side of the heating; when faulty it defaults to full flow, probably one side of yours is faulty therefore constant hot flow , to check disconnect power lead at duovalve then both sides should run hot no matter where temp.controls are set.
See here, http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1SL15BCKH1SL15C9I7&year=1998&make=MB&model=E-320-005&category=R&part=ACC+Mono+Valve.
Geo

Thanks Shandy for the first input that makes sense. I knew I didn't have a leak or was not low on charge, as my compressor turns and stays on all the time. Other ac guys also suggested the heater valve, i was just looking for re-assurance. I allways ask for multiple opinions. If there is anything else you can think of, please let me know. Thanks again.

My parents S class did this about two years ago, changed the likely culprit the water valve as mentioned by Shandy. In our case it did not fix it.

The problem was Mom on the passenger side was aiming the cold air away from her and the cold air was blowing onto the temp sensor triggering it to blow warm on her side only.

It probably is the water control valve like Shandy says but check the vent aim first.

What part of our advice regarding charging doesn't make sense? I have personally experienced the issue you described, and it was in fact "cured" by a $7 can of refrigerant from Wal-Mart. Due to the variable displacement design of the A/C system in the 210, the evap can put out a warmer temp to the driver vent if the charge is low. Usually if middle is cool and both outer are warm, it's the duovalve. If warm on driver's side and progressively cooler towards passenger side, it's low refrigerant charge. This is a very, very common problem. Of course it is also entirely possible that the duovalve is bad - if you want to throw more money at the problem be my guest.

I told you to do a search, did you? Well I did - look HERE. This is just one thread - if I had the time to search properly I could come up with 20 or 30 threads that detail this exact problem being caused by a low charge.

You got multiple opinions but only accepted the one you wanted to hear. Why be so quick to discount advice that you asked for? With only 3 posts it's obvious you're new to this forum and I suggest SEARCHING and, above all else, if you're going to ask for advice then it might not hurt to listen to others who have been there done that. Oh, by the way, whatever the fix ends up being, please report back so you can help others in the future who do a search on this topic.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Thanks for the link gmeroleza, however, the thread you linked me to explains that low charge was NOT the problem.

You are correct, low charge was NOT the problem. But then the problem wasn't exactly like yours, was it? READ IT AGAIN:

Notice, his symptoms were hot/warm air on the outboard vents, nice cold air on the center vent. This is not the same problem you are having. Per your description:

Your symptoms are entirely different. Warm on driver's side, and progressively cooler towards passenger side. You never said anything about cold air on the center vent. Are there some details you haven't told us?

I consider stevebfl to be one of the resident A/C experts. Notice what he says, which backs up what I said:

Notice, he says "I have had the dual heater valve cause the outsdie ducts to be warm." Again, I will repeat: Usually if middle is cool and both outer are warm, it's the duovalve. If warm on driver's side and progressively cooler towards passenger side, it's low refrigerant charge.

It's obvious I'm not gonna convince you. Go ahead and order the valve for $166 + shipping, and let us know if it works.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Dear gmercoleza, obviously I'm gonna check the charge first. If my charge is sufficient, I'll change the duovalve. If my charge is low and after re-charging my probles go away, I will not replace the duovalve obviously. Thanks for your thorough inputs. I will keep you gentlemen posted.

95% of the time when i see this same issue it is low freon, definately start there first.

Dear friends,

I've gauged my AC charge this morning, the reading was over 50psi= full.

Guess I should move on to changing the duovalve?

Connecting a charge hose isn't the answer...have the system discharged & PROPERLY recharged with the correct weight of refrigerant!

50PSI means little OR nothing! a normal system at rest at a temp of 70-80F will read at least 100psi. but again it isn't all about pressure but about correct refrig charge by weight!

YOU description sounds like a LOW charge of R134a not a bad valve!

__________________
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