brasil

Here's another issue that has spoiled my summer in NYC: I can't seem to ever get the A/C to blow ice cold. I've done the requisite searching of the threads, and my best (albeit amateur, non-mechanic) guess is that this might be the Duovalve issue that Marcus writes about here: http://www.marcusfitzhugh.com/CLK/DIY/duovalve.html

Here's the readout from the REST function on the HVAC panel after 30 minutes of driving, outside air temp 83 degrees F. Values 3, 4, and 5 look fishy to me based on what others have posted for these values. 116 degrees at the evaporator sensor can't be normal under these conditions, and the heater core temps should be a LOT lower it seems:

1 - 92
2 - 110
3 - 84
4 - 85
5 - 116
6 - 203
7 - 16
8 - 115
9 - 13
10 - 3.4
20 - 4.3
21 - 6
22 - 0
23 - 0
24 - 13.9
40 - 8
41 - 5
42 - 232
43 - 14

What's going on?

brasil

Today I opened up the duovalve just to take an exploratory look, without really having the tools lubricate or clean it. Now that I think of it I should have taken a picture, but basically the dual metal caps that come off (that are connected to the electrical feed) have a plastic piece inside them that matches the diameter of two plungers mounted on springs that sit in the bottom piece. Everything was soaked in what I assume is engine coolant since that's what flows through the valve.

The plungers were in what I assume to be the up (open?) position - they're sitting on springs, and that seemed normal but I can't be sure. Nothing seemed "stuck." Is the valve held closed by an electromagnet inside the cap? Is "open" the default state?

I checked the values of the REST diagnostic again today and the values were pretty much the same as what I posted. Would love some input on this. Meanwhile I'll post to the thread here: http://www.eclassbenz.com/

MarcusF

I don't think its the duovalve. I think your evaporator sensor may be shot. The evap sensor is #5 and should read either a little below ambient temperature (before the AC is working) or much colder. Yours is 116 degrees, while the in-car temperature sensor reads 92. Unless it’s really 116 in your car, the evap sensor reading is way off (over 25% high). Although your heater cores are hot (mid-80s), I think that’s because it’s 92 in your car.

The evap sensor is part number 2108300772 and is sold at internet MB parts dealers for $67. Based on threads from others, it is a DIY swap and doesn't take much time. There was a thread 5 years ago or so by a guy with a bad evap sensor. His also read high and the interior never cooled down. He swapped the sensor and that fixed it.

If my car is normal, my evap sensor normally shows something in the mid-30’s and the heater cores are in the 40s.

brasil

Thanks Marcus, your opinion is highly valued. I don't think I can go wrong buying an evaporator sensor at this point.

The only other value that's puzzling is why the outside temp sensor (#2) is reading so much higher than the actual temperature, including what the dashboard display reads - apparently the dash temperature display gets its reading from somewhere else?

I just checked it again and the HVAC diagnostic throws 92 for #2 (outside temp) while the dash display reads 83. This was while parked and after idling with the A/C on for 10 minutes. When I wrote down the original numbers the discrepancy was even higher.

wozy230warren

Hi guys,

I just bought a 230 w208 and seem to have an issue with the A/C not blowing cold enough. What can I check? How did you generate those numbers on the first post?

Any help would be most appreciated.

Best

Woz