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  #61  
Old 06-17-2018, 01:38 PM
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The NTC thermistor increases resistance as temperature falls. If it is open circuit, the PBU thinks the evaporator is at an extremely low temp.

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  #62  
Old 06-20-2018, 03:18 PM
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Quote:
Originally Posted by Diseasel300 View Post
The NTC thermistor increases resistance as temperature falls. If it is open circuit, the PBU thinks the evaporator is at an extremely low temp.
My sensor was about 14.00 ohms. I got another one - new style W201 that is has the metal casing and ohms at just under 7. I tested them both at the same time, same outside temperature.
Still no compressor kicking on.
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87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
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  #63  
Old 06-20-2018, 10:42 PM
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You have a PBU problem from the sound of it. You already know that grounding the pin at the PBU turns on the clutch, you know the Evap sensor is good, the PBU is all that's really left at this point.
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  #64  
Old 06-21-2018, 09:56 PM
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Quote:
Originally Posted by Diseasel300 View Post
You have a PBU problem from the sound of it. You already know that grounding the pin at the PBU turns on the clutch, you know the Evap sensor is good, the PBU is all that's really left at this point.
I got the PBU already sent out via UPS. Stay tuned for the installment!
__________________
---------------------------------
87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
07 E320 Bluetec
12 S350 Bluetec
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  #65  
Old 07-07-2018, 03:21 PM
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This has become a nightmare.....
Okay so the first set of replacement PBU arrived in a box that was driven over, the tire print looks like a forklift tread, not joking. Contents smashed. ( Never use the USPS for anything of value! )
Next replacement send via UPS. Box looks good. Strike 1 - all the airflow buttons are depressed?! Strike 2 - there is a rattle inside if you shake it. Not like its something completely loose and rolling to one side to another but as if its contained in a small area, like a a baby toy rattle.
What a heck lets try it. I push around the buttons some and they spring back out.
Plug it in.........................Strike 3 - Still. No. Compressor.
Helppppppppppppppppppppppppppppppppppppppppppppppppp!
__________________
---------------------------------
87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
07 E320 Bluetec
12 S350 Bluetec
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  #66  
Old 07-09-2018, 07:00 PM
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Is there any other way to test the PBU and or the ground as to where it grounds the A/C compressor clutch?
__________________
---------------------------------
87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
07 E320 Bluetec
12 S350 Bluetec
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  #67  
Old 07-09-2018, 07:58 PM
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You already tested all the wiring up to the PBU and it'll engage the compressor when grounded. That rules out everything up to the PBU. There's something in the PBU that's preventing engagement, that's as far as I'm useful in helping on this matter since I'm not familiar with the operating conditions of the W201 PBU.
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  #68  
Old 07-09-2018, 08:15 PM
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How about where does the PBU get its ground from?
__________________
---------------------------------
87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
07 E320 Bluetec
12 S350 Bluetec
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  #69  
Old 07-27-2018, 12:46 PM
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Okay so the better part of this month was wasted with trying to get PBU delivered to me - in one piece. From the first vendor I got 2 damaged ones and a third that was lost in space never sent. Now I got a quality set from George at Performance Analysis.
However- I still have no compressor engagement in any setting, defrost too.
Now all the other functions work: dash air going where it should, fan speeds.
**** How about where does the PBU get its ground from?
__________________
---------------------------------
87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
07 E320 Bluetec
12 S350 Bluetec
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  #70  
Old 09-30-2018, 02:49 PM
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Quote:
Originally Posted by Diseasel300 View Post
You already tested all the wiring up to the PBU and it'll engage the compressor when grounded. That rules out everything up to the PBU. There's something in the PBU that's preventing engagement, that's as far as I'm useful in helping on this matter since I'm not familiar with the operating conditions of the W201 PBU.
Just like to say thank you to you and everyone else that gave some input on this Major headache.
Also Performance Analysis | Climate Control | Diaphragms | Blower Motors | Pushbutton Panels | Vacuum Door Locks | Autotemp | Cruise Control | Engine Oil Analysis | Mercedes-Benz Parts | Mercedes-Benz Club of America | Oak Ridge | Car Care is a great company.
I had to find an independent shop that would test out this car. https://www.facebook.com/autowurksdiesel/
It even took them a long time but they found it and had to use the test cables brake out box for the W201.
**** PROBLEM SOLVED!
Turned out to be a poor solder joint connection in the right side / passenger side harness of the push buttons unit that came from the a temperature sensor. When the push buttons were exchanged sometimes - just sometimes - the A/C would work for a bit and then gone. It did not look obvious and was only found using a meter.
I'm ecstatic this car is now 4 seasons capable!
__________________
---------------------------------
87 300SDL
87 190D 2.5NA 5sp
90 300GD with 606 turbo!
08 GL320 CDI
12 ML350 Bluetec
---------------------------------
Past rides:
82 300SD - the one that started it all!
81 240D
87 300SDL - the first one.
92 300D 2.5 Turbo
99 E300 Turbodiesel
07 E320 Bluetec
12 S350 Bluetec
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  #71  
Old 09-30-2018, 03:07 PM
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The craptastic German soldering skills claim another victim!

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