AmirB

Hi. I had issues before that the AC stared to blow warm air and was fixed by adjusting the temperature but yesterday after driving for 40 minutes I made a short stop. After starting the car I noticed the left vent was blowing hot air and center and right vent blew cold. I could not remedy the problem by lowering both side temp control to LOW. Drove to work and parked. last night everything was fine on the way home. Today the same problem, after the short stop. I would appreciate any help. Car is E420 1997.

here is the diag readout from the AC display
1 -24 in car temp
2- 36 outside temp
3-74 heater core temp left side
4- 24 heater core temp right side
5- 02 evap temp sens
6- 93
7- 11 ref. pressure
40 - 71
41- 34


Regards

Amir

HTBenz

Just a guess but I bet it is that you have low pressure in your A/c system. Meaning you need R134 in your system. mine did the same thing and that was the problem as it was for a lot of other people.

lexrex

Your evaporator temps & pressures look about normal. It looks like your heater duovalve is sticking on the left side. Notice that your left side heater core (#3) is considerably warmer than the outside air (#2). Low refrigerant pressure can cause the left side to blow warmer air than the right side (#4), but in no case will low pressure cause the air on one side to be warmer than the outside air. Your problem is that the left side heater is stuck on.

The duovalve controls how much hot engine coolant circulates through the left & right heater cores. If it sticks open on one side, it'll heat the air passing on that side. I would expect cold air to blow out of both sides and warm gradually out of the left as the engine warms up.

Sometimes tapping the valve with a screwdriver loosens it up. If it sticks regularly, you'll need a new valve. If you don't feel like fixing it, close the vent on the left side by the door. If your diverter flaps are working properly, the left-center vent should blow cold air without passing through the heater. Good luck!

The duovalve hasn't been discussed on this forum, but the folks on BenzWorld have talked about it. Here is some additional reading material from the BenzWorld forum:

• Climate problems blows hot and cold
• AC Problems on e320 2000
• Why would one A/C vent blow cold and not the others?

AmirB

Thank you Blake. I will try to find the duovalve and follow the instruction of lubricating them. I should run the flap test too! When you say the right side of the car is that the passenger side?

Regards

Amir

Osman

I own an E320, 2003 model with similar a/c cooling problem like the one mentioned above (i.e cooling from the passenger side while blow hot air from the driver side's two vents). But mine seems to loose its coolant suddenly after about 3 to 4 days. Checks by a/c attendant revealed no leakages! I can understand valves malfunctioning but where does the coolant always leak into? I also notice a small rapture on the outside hot air hose linking the engine cooling system but the a/c man keeps telling me it has nothing to do with the loss of the coolant. What do you think is really the problem?

PelicanParts.com

This may help you.

http://www.pelicanparts.com/techarti...trol_Valve.htm

roy@peachparts.com


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