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#17
11-07-2010, 01:18 PM
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After doing more reading and testing, I found that the green capped sensor is the Aux fan switch, and bridging the wires kicks the fan on.
The pressure switch below it has no voltage at either wire... which is a VERY good reason why the A/C is non functional! I looked at the wiring diagram, and I am struggling to trace the power back... Is the Klima relay at fault, a fuse or wire, or the control panel? Help!
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2009 Mercedes ML320 Bluetec 
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#18
11-07-2010, 07:21 PM
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Only when the A/C is on and that in turn gives voltage to your aux fan for low speed. I suggest you check strip fuse at firewall if you have the TSB installed and the resistor block for the fan under the ABS pump as a broken or bad connection or a blown fuse will cause the A/C not to kick in. By jumping your pins your bypassing that pressure switch (green is the correct color for your year). Red is not actually a pressure switch but a temp switch called a pressure switch. If the fuses and resistor block are good then it may be the relay.
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#19
11-08-2010, 04:56 AM
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The red one is a pressure switch that activates the aux fan on low speed. This can be confirmed by checking the EPC to see that it specs these switches in pressure units, not temps. It works the same as the green one, but at slightly higher pressures (20/15 vs 16/12, IIRC).
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1988 California version 260E (W124) Anthracite Grey/Palomino Owned since new and still going strong and smooth MBCA member Past Mercedes-Benz: 1986 190E Baby Benz 1967 230 Inherited from mom when she downsized 1959 220S Introduced me to the joys of keepin' 'em goin' There are only 10 kinds of people in the world--those who understand binary and those who don't
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#20
11-11-2010, 05:22 PM
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The one thing that I was concerned about was that the Tach was not working... and I was thinking that this could have been an issue.
I got the Tach working today, and I still have no voltage at the pressure switch. Checked the fuse in the fusebox and its good. Is the a fuse somewhere else? At this point I am chasing why I have no voltage at the pressure switch... without power there there is no way the A/C is gonna work. Ideas?
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2009 Mercedes ML320 Bluetec
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#21
11-11-2010, 05:26 PM
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Quote:
What is the TSB?
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2009 Mercedes ML320 Bluetec
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#22
08-03-2011, 12:11 PM
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Time to get this A/C working, and revive this thread!
Updates: Tested Static pressures yesterday and they are as they were before... about 100psi on this 95degree ambient day, so as I charged it over a year ago, and it has not worked, we can assume the system is leak free! The tach is working again now.. It was a loose cable in the cluster. I was checking yesterday, and found the a cable broken off a temp sender on the front of the Cylinder head, so fixed that. I have a problem with the Temp sender on the side of the thermostat housing that also controls the Aux fan... the cap is broken off that, so I wedged it on so it runs. Now, I recently bought this off Ebay in the hope it would help me....  Here are the instructions...  Now despite what it says, there is no switch that I can find on the unit for post 85 cars...  A call to Baum Tools was no help... nobody knew anything about it... the Instruction sheet is dated 1997. Decided to try it... Now the Klima Cable fits between the klima Relay and its socket... Interesting.. With it all plugged in and Engine running it looks like this:  Pressing the gas pedel causes 87Z LED to go off... I took the reading for each pin like this...  All readings taken with my DMM with - probe in #31 on the Monitor engine at idle with A/C on max. #15 = 10.75V #TD = -0.85V #GK+ =-0.85V #87 = -0.885V #T =11.15V #KL =0.5V #87Z =9.5V Any thoughts or ideas?
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2009 Mercedes ML320 Bluetec Last edited by Merkey; 08-03-2011 at 12:31 PM.
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#25
08-04-2011, 10:38 AM
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Thanks DS, got it!
I will try to get some more readings and work thru the flowchart today... Member Alder said this over on the thread I started about the Klima Monitor.. "pin # 87 indicates there is no power going to the compressor.It should have battery voltage KL pin is compressor enable ; does it have a change in voltage from max cool to max heat setting ? i assume it should to enable the relay to activate compressor" I will check that too and post results.
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2009 Mercedes ML320 Bluetec
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#26
08-05-2011, 10:33 AM
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Looking at my readings again...
#15 = 10.75V #TD = -0.85V #GK+ =-0.85V #87 = -0.885V #T =11.15V #KL =0.5V #87Z =9.5V Anyone know why I am only getting 10.75V from pins #31(earth) to #15 that should be battery voltage?
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2009 Mercedes ML320 Bluetec
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#27
08-05-2011, 10:04 PM
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Found this which makes interesting reading...
http://www.cacavas.com/mb/TTM.html
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2009 Mercedes ML320 Bluetec
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#28
08-05-2011, 11:33 PM
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How to test a Klima unit .
My 300SE 126 has a red unit ,bridging this gets the fan activated which normally kicks in after a minute ,still not sure if its temperature or pressure activated, the other switch is not color coded .
In my car I suspect the Klima unit is inoperative as bridging the pins activates the compressor ,the electric fan comes on after a minute and the cooling is rapid. Time to source a new Klima unit? Regards Ad
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#30
03-15-2012, 07:52 PM
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Ok, time for an update on this saga and some REAL progress!
I have the Diesel in my garage and have been doing service stuff. While its up on the ramp, and fluids are draining, I decided to do some investigation work. I had obtained a working Klima relay, and installed it to no change. Working thru the FSM, and the first check is that an 1984MY should have battery voltage at the Blue/White wire(red arrow) of the Pressure switch. I have no voltage, so it says to check the wiring diagram.  I am lucky enough to have recently bought a great tool... A Powerprobe ECT2000 wire tracer..  Having pluggesd in the unit at the Blue/White wire at the pressure switch, I followed the signal along the harness, under the LH headlamp, up and along the LH inner fender, thru the firewall and into the fusebox area.. and there I found something.... Blue Arrow is the Blue/White wire from the Pressure switch... And its been cut off and jointed to a white wire... which disapeared under the fusebox. The original piece of the Blue/White wire is arrowed in red, where it is still connected to the fusebox!  Worked at pulling all the wires off the fusebox... Now I see the white wire.. It comes down into the underdash area, and is jointed to a Blue/Green wire that looks like it was cut off from somewhere...  The Blue/Green wire is a factory wire, and is bundled with the wires that are going into this plug that is in my hand...  Now, I feel like I made some progress! My question is this.... This Green/Blue wire that is now connected to the pressure switch... What the hell was it connected to? What is also odd, and maybe connected... I have no full beam lights, and also teh Cruise does not work... Just occured to me that maybe these 2 issues are connected??
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2009 Mercedes ML320 Bluetec
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