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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #1
My CLK 500 doesn't have any heat. The blower motor is operational at all speeds, but the cabin temperature does not change despite whether I raise or lower the temp settings.

I'm reasonably certain the blend door is not working, but I do not know where it is located or how to test it on the W209. Also, I believe the auxiliary water pump works in conjunction with the blend door (although admittedly I am not certain), and I did install a new pump on my car when I first bought it a few months ago, and I'm thinking that pump might have some role in this no heat issue too.

Could someone point me in the right direction, i.e. where the blend door is located, test parameters, voltage specs, etc. Any voltage specs pertaining to the auxiliary water pump will also be appreciated.
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #2
Bueller ... anyone ... Bueller

Here's my update. I read about auxiliary water pumps since my original post, and I believe the car would still have heat even if there was a problem with the auxiliary water pump. Since my car has no heat at all, I feel the pump is not the problem.

I see that some Mercedes have blend doors, whereas others use a "heater control valve" (something I've never heard of before but it apparently takes on the same role as a blend door). After my original post I found that the W209 uses a heater control valve, but if anyone has any knowledge on troubleshooting this and other parts of the W209 heater system, I'd be grateful.
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #4
I'm going to begin dismantling the heating system components tomorrow so I can figure out how it works and fix my issue. Although your problem is a bit different, I'm sure there is only one part of the system that would cause both hot and cold air to blow at the same time. Perhaps the heat actuator? I'll let you know what I find out after I work on my car.
 

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2004 CLK 240 Coupe
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11,377 Posts
Working on minimum information here....:confused:

I think that the Convenience (or Comfort) Automatic a/c sytem (CODE 581b) was standard to later CLK 500s, but I'm not sure it was in 2003. If you have a digital display window, you can read out diagnosic values that can help with a/c faults. You can certainly establish if hot coolant water has left the heat exchanger and entered the a/c unit. I will post the instructions here to do that if required.

With the engine cover removed, you will be able to touch the hot water hoses to/from the engine and the heat exchanger located behind the dash. This would establish if this circuit is working. There are separate blender flap motors for left and right ducts. It's hard to believe that both motors have failed together.

Also what do you mean by the 'auxilliary' water pump? There is only one water pump; the one that drives the coolant through the radiator. You cannot run the engine (safely) without it. :eek:

Here is the coolant water circuit.
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #6
Thanks for that information. Aside from the water pump that sits on the engine block (the one you referred to), there is also a second water pump on the CLK (i.e. auxiliary water pump). It's mounted on to the coolant expansion / coolant recovery tank. Its only purpose is to keep the water circulating through the heater core at a constant rate irrelevant of engine RPM. I find it interesting that the diagram you posted does not include that as part of the system, but I also see the diagram says "coolant circuit illustrated on engine 112" so perhaps that it is a new feature on the 113 engine. I'll attach a generic picture of the pump.

I have eliminated the pump as the problem; I put my hand on the hoses coming off the auxiliary water pump and I can feel the coolant circulating through the hoses. As you suggested, I removed the engine cover and the hose going from the block to the heater exchange is hot, as is the hose coming from the heat exchanger to the auxiliary water pump.

I feel the observations above eliminate the heat exchanger, as well any component shown in the illustration you attached. Therefore, it appears the blending air flaps are the problem, which the illustration mentions, but does not illustrate. I also need to say that when I went outside to feel the hoses, I also just recognized that I am not able to operate all vents in the car despite changing the buttons on the digital display: the back seat vents are good, the front defrost vent does not work, the driver's floor vent always has air pumping out regardless even if directed not to, and the dash vents are weak.

Any input? Do you have a diagram of the heater assembly that contains the blending air flaps? Thanks for the feedback.
 

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2004 CLK 240 Coupe
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Hi - I might be able to help a bit more...

Delving deeper into the WIS I have now found references to additional water pumps for 2 applications on the CLK range, neither of which are shown on the standard coolant diagrams. I have also found a coolant circuit for the M113 engine, which shows the duovalves that I presume you have. M112 does not have these. See pdf below.

a) is for something called 'stationary heater' (CODE 228) which has its own combustion system, complete with fuel lines, etc. (wtf??)

b) is for a coolant circulation pump (CODE 874) which might be something used before the introduction of the REST feature: Residual Engine Heat Utilisation, which is on my 2004 CLK a/c system. Otherwise, I cannot figure out how it is used in practice. :confused:

I use the REST facility to obtain blown heating with the engine switched off. The standard water pump (M13) runs, and the a/c blower is set to 25% of its output.

Regarding the actuator diagrams, I do not know if you have the 'automatic' or the 'convenience' a/c system installed, so I have posted drawings of both.
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #8
Thanks for the diagrams.

I am now certain the problem is narrowed down to the duovalve or the actuators. There doesn't appear to be any way to absolutely rule either one out since they both control the heat/cold air introduced into the cabin.

I will focus on the ac/heater assembly that houses the actuators first, and the duovalve second (if needed). My rationale: since I am unable to redirect the air flow to different vents despite changing the buttons on the digital display, it appears there is something going on with that assembly, in addition to the inability to adjust hot/cold air. I think the thing to do is to visually see the behavior of the actuators when I push the buttons on the digital display and work from there.

I will post the results, although I may not have the opportunity to work on the car until later in the week. Thanks again.
 

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2004 CLK 240 Coupe
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Hi - You seem to be narrowing the problem - good.

You forgot to reply about your a/c unit display. If you have the version with a display window, you can get some basic readouts of the conditions inside the a/c unit with the diagnostic facility. :thumbsup:
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #10
I am attaching a picture of the digital controls on my dash. It would be great if this display could tell me if the duo valve or actuator was the culprit. Nonetheless, even if it does not indicate what part is faulty, I would still like to know how to use the display to check the AC/heat system. Thanks!
 

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2004 CLK 240 Coupe
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Good! Your a/c system is exactly the same unit that I have. It's the Comfort Automatic A/C system code 581b.

Here are the instructions for getting the diagnostic data from the unit. I can vouch for the instructions for reading the sensor data, as I have done this myself. I have never read the error codes.

I am not the author of these instructions, which were written for an E class MB. - I have simply saved them.

-----------------------------------------------------------------------------------------------------​

Part 1 — Collect Sensor Data

First we’ll get the values of all the various climate control sensors. These sensors constantly monitor data like air temperature, refrigerant pressure, etc. Odds are if something’s wrong, a sensor will pick it up. Let’s get started!

Start your car.
Press the “AUTO” button on your climate control.
Turn on the A/C (i.e. “EC” light must be off; if the light won’t shut off, continue with this test. We’ll address your “EC” light on the next page.)

Let the car idle for about 3 minutes.
Set the temperature on each side to 72°F. You can do this quickly by pressing both the red and blue arrows simultaneously.

Press and hold the “REST” button for five seconds or until the left side of the display says “01.” The left side indicates which sensor you’re checking. In this case, #1 is the in-car temperature sensor. The right side of the display shows the value of sensor #1 (in this case, the actual in-car temperature).

Press the “AUTO” button on the left side to move to the next sensor. Press the “AUTO” button on the right side to move to the previous sensor.

Record the ID number of each sensor (left side of display) and its corresponding value (right side of display). You only need to do this for sensors #1-8. You can write down the values for the other sensors, but they’re not really related to air conditioning function.

When you are done, press the “REST” button again to exit the self-check mode.

Part 2 — Collect Trouble Codes

Now that we have all the sensor values, let’s check the computer for malfunction codes. Read this carefully, because you have a 20 second window after switching on the ignition to load the trouble code display mode.

Ignition must be switched on. 20 second timer starts.

Increase the left side temperature (left red arrow) until left side says “HI.”

Decrease the right side temperature (right cold arrow) until right side says “LO.”

If your 20 seconds passed, switch off the ignition and switch it back on. Your HI/LO settings will be preset. Timer restarts.

Press and hold the “EC” and “REST” buttons simultaneously for at least five seconds. The screen will go blank.

Load the first code by pressing the right side “AUTO” button.

Write down each error code. To cycle through the codes, press the right side “AUTO” button.

When you finish, press the “REST” button to exit.

Part 3 — Submit Your Sensor Values & Trouble Codes

A/C Sensor Values

Enter the values from each sensor.
Sensor 1 - Inside Temperature:
Sensor 2 - Outside Temperature:
Sensor 3 - Left Heater Core Temperature:
Sensor 4 - Right Heater Core Temperature:
Sensor 5 - Evaporator Temperature:
Sensor 6 - Engine Coolant Temperature:
Sensor 7 - Refrigerant Pressure:
Sensor 8 - Refrigerant Temperature:

Error Codes:

Error B1226 - In-car Temperature Sensor Malfunction
Error B1227 - Outside Temperature Sensor Malfunction
Error B1228 - Left Heater Core Temperature Sensor Malfunction
Error B1229 - Right Heater Core Temperature Sensor Malfunction
Error B1230 - Evaporator Temperature Sensor Malfunction
Error B1231 - Engine Coolant Temperature Sensor Malfunction
Error B1232 - Refrigerant Pressure Sensor Malfunction
Error B1233 - Refrigerant Temperature Sensor Malfunction
Error B1234 - Sun Sensor Malfunction
Error B1235 - Emissions Sensor Malfunction
Error B1241 - Refrigerant Low
Error B1416 - Coolant Circulation Pump Malfunction
Error B1417 - Left Duovalve Malfunction
Error B1418 - Right Duovalve Malfunction
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #12
That is impressive. I was able to move through the "Collect Sensor Data" section, but the "Collect Trouble Codes" isn't applicable to the newer generation. I am unable to complete the step: "Press and hold the 'EC' and 'REST' buttons simultaneously for at least five seconds" because we don't have an EC button on the display. Logic would suggest that the new generation should have the capability to "Collect Trouble Codes" if the digital readout can "Collect Sensor Data" as previous generations. I just cannot figure out what buttons to push to enter into trouble code mode. I think I will play around with the display a bit and see if I can figure it out. According to the trouble code definitions you provided, it will tell me if the duovalve is operating properly ... if I can just figure out how to enter into trouble code mode. Thanks again.
 

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2004 CLK 240 Coupe
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11,377 Posts
According to the trouble code definitions you provided, it will tell me if the duovalve is operating properly ... if I can just figure out how to enter into trouble code mode. Thanks again.
If its any consolation, I also failed to figure out how to get the trouble code to work with the buttons we have. I'm sure its possible.

Let's hope someone who knows posts the solution here...:)
 

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2004 CLK 500, 2011 C300 4Matic
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Discussion Starter #14
Fixed.

Today was the first day I had available to work on the car since my last post ... you know how life goes. I began by removing the glove compartment and the CD changer so I could have a good look at the actuator movement when changing vent directions on the digital display. The only movement was rotation of the blower motor. There was no movement of the actuators. I thought a bit more about what you had said: "There are separate blender flap motors for left and right ducts. It's hard to believe that both motors have failed together."

It then occurred to me that I had removed the digital display panel a few months ago in order to reset the airbag control module during the rebuilding process. So I now began focusing my attention on digital display itself. I removed the center console and sure enough, I found a three pin connector unattached (there is a 10 wire connector on the back of the digital display that I had connected, but I apparently neglected to attach the 3 pin connector :bash:). I connected the 3 pins to the back of the digital display -- instant heat and vent movement. :)

Time to go back outside and start putting the car back together. Thanks for your help again, much appreciated.
 

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2004 CLK 240 Coupe
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11,377 Posts
Well done - that's good news, I was wondering how you were progressing...:)

We have both learned a lot from this excercise. Every time I delve deeper into the WIS I find something that I had no idea existed - your additional circulation pump, for example.

Enjoy your newfound heat...:thumbsup:
 
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