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Discussion Starter #1
After spending many hours banging my head against a wall, reading what seemed like endless forum's about climate control problems and getting half a dozen different answers to what seemed like the same problem... I have decided its a good idea to help the next guy out. So the two following .pdf files are how to diagnose your climate control problems with no special tools what-so-ever. All you need is a piece of paper and a pen. The first file you should run is the "scanning sensor values". This will first let you know if any of your sensors are bad which might be throwing off your system. If everything checks out there run the "fault memory" file. A word of advice on the directions on "step 1 and step 2" engaged means that the wheel is all the way locked on high or all the way locked on low not just somewhere in the red or blue zone. When I ran mine the first time I had a ridiculous amount of errors (since the car is 16 years old and apparently no one ever cleared them before) so I deleted them all, ran the car for 10 minutes then re-ran the test. I then had just 4 errors. When you go to delete errors you must do steps 1-5 first then do step 9. Also, before each code deletion you must press the "left auto" button before pressing the "right auto" button. Keep doing this until the display reads "E0 00". After you run these 2 files you will know exactly what is wrong with your climate control system without spending a penny.
 

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1995 S320
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Heater blows cold

Thanks for the info, I have been struggling with this too. The sensor values still have me puzzled. My outside temp readings (#2) are in the 60's & 70's when the dash temp is in the 30's. Also, my heat exchanger temps are in the 30's & the car is warmed up.
My inital problem is the heat blows cold air and I am desperately looking for a fix. I picked up a used duovalve & electric pump but would like to know that is the problem before I make that repair.
Any help will be greatly appreciated.
 

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W220 S320 CDI 2005; W140 S280 1994 (Sold Nov. 2012)
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Thanks for the info, I have been struggling with this too. The sensor values still have me puzzled. My outside temp readings (#2) are in the 60's & 70's when the dash temp is in the 30's. Also, my heat exchanger temps are in the 30's & the car is warmed up.
My inital problem is the heat blows cold air and I am desperately looking for a fix. I picked up a used duovalve & electric pump but would like to know that is the problem before I make that repair.
Any help will be greatly appreciated.
Suggest you post a full set of sensor values (plus the dash external temp. value), recorded when the engine is warmed up and the a/c is on. Set the left and right temperatures to be around 22degC (72 degF). Personally, I find it easier if the temps are posted in degC but I can do the conversion.

Mike
 

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1995 S320
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W140 Climate Control Problems

Thanks Mike,
Here are the previous readings.
The engine was warm with function buttons set to Auto, temp in the white area.
I will do it again with the left and right temperatures to be around 22degC (72 degF).
Here's the list:
Degrees F Degrees C

1 48 9
2 62 17
3 40 4
4 39 4
5 38 3
6 00 -18

7 09
8 28
9 20
16 0

Thanks
 

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W220 S320 CDI 2005; W140 S280 1994 (Sold Nov. 2012)
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Thanks Mike,
Here are the previous readings.
The engine was warm with function buttons set to Auto, temp in the white area.
I will do it again with the left and right temperatures to be around 22degC (72 degF).
Here's the list:
Degrees F Degrees C

1 48 9
2 62 17
3 40 4
4 39 4
5 38 3
6 00 -18

7 09
8 28
9 20
16 0

Thanks
So it looks as though the compressor and a/c side of the system is working OK: #5 (evaporator temp) is OK at 5 degC (should cycle between 2 and 6 degC) and #7 (refrigerant pressure) looks OK at 9 bar.

The '00' for #6 (engine coolant temp.) is actually either 100 degF or 200 degF, depending on how warm the engine was: the display can't show the third digit, which is one of the reasons why switching to degC readout is handy. Alternatively, it could be that the ECT sensor is nbg but I doubt that - you can always check what it says when the engine is cold and decide whether the sensor's OK.

Without knowing what temperatures had been selected (left and right) it's difficult to assess whether the duovalve and/or pump is your problem but it certainly looks like one of them. The left and right heater core temps (#3 and #4) at 4 degC are very close to the evaporator temp of 3 degC, indicating that no hot engine coolant is being supplied to the cores, either because the temps have been set very low or because the pump/duovalve is not working. If #3 and #4 stay low when you select 22 degC left and right, then that points to the pump/duovalve.

Anyway, that's how I read the situation - but have been known to be wrong!

Mike
 

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Discussion Starter #6
The way I checked mine was pull the connectors off the circ pump and duo valve (carefully!!). Check the resistance of the circ pump @ the circ pump(should be 2-4 ohms) then with the ignition on and the temp selectors engaged in red check the voltage of the connector @ the connector (should be between (11-14v) then with the temp selector engaged in blue (should be less than 1v). Do the same thing with the duo valve. Resistance should be between 20-35 ohms and the voltage values are the same as the circ pump. This test will tell you if the problem is with the circ pump, duo valve, wiring or the control unit. "Example": if you get an open reading (no resistance) at the duo valve, a 11.4 volt reading with red engaged and a 11.4 volt reading with the blue engaged you have 2 problems the duo valve is bad and the climate control unit is bad but the wiring is good.
 

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mike

i have a 02' 320. it blows cold air when motor and ambient temp is cold. i got e61 on left and 231 on right side of screen on error check. is this a bad sensor?

thanx
 

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W220 S320 CDI 2005; W140 S280 1994 (Sold Nov. 2012)
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mike

i have a 02' 320. it blows cold air when motor and ambient temp is cold. i got e61 on left and 231 on right side of screen on error check. is this a bad sensor?

thanx
Sorry, I don't know anything about W208s but I see from your other posts that you think that your ECT (engine coolant sensor) may be bad. If you run the sensor test (I assume a 208 has this) then you can read the ECT value and see if it makes sense.

Mike
 

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i guess it's possible if it doesn't know how warm the engine is, to start blowing wide open. its too damn cold in the mornings for that. i guess i'll have to use it manually
 

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Discussion Starter #10
mike

i have a 02' 320. it blows cold air when motor and ambient temp is cold. i got e61 on left and 231 on right side of screen on error check. is this a bad sensor?

thanx
Have you run both tests listed at the top of this thread?
 

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which w140's will this work for? I have a 97 s420. I cant quite figure out how to get into diagnosis mode.
 
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