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  #1  
Old 08-23-2015, 02:52 PM
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Angry A/C compressor 91 300D

Converted from R12 to R134a. I replaced the compressor, new accumulator/drier, new low pressures switch, new temp switch, new climate control unit, new low and high pressure line adapters for R134a and I still can't get refrigerant to fill the system. I have an a/c manifold gauge set... evacuated the system, but each time I try to fill the system it seems as if the low pressure line fills with refrigerant, but the compressor clutch never engages....therefore I never see refrigerant in the sight glass on the accumulator dryer.

To me something is preventing the refrigerant from entering the system....

I tried jumping the low pressure switch, the aux fans come on, I hear the relay click, but the clutch doesn't engage,

What am I missing? Could the expansion valve be the culprit?

All electrical connections are securely fastened and no bad fuses...I'm at a loss...
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  #2  
Old 08-23-2015, 03:01 PM
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Exactly where are you trying to input the refrigerant ?
Did you flush your parts before putting all those new parts on ?
What exactly is a ' climate control unit ' ?
Why did you change from R12 to R134a ?
Was the AC working before you started this change over ?
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  #3  
Old 08-23-2015, 03:10 PM
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Climate control unit....the push button unit in the console
A/C stop working on R12 refrigerant a few months ago...had old refrigerant, recovered....tried conversion on my own.....

I've successfully replaced compressors and other a/c parts before on Chevys, Pontiacs, 87 300D...

when you say flushed new parts....what do you mean?

I followed the instructions on the compressor...kept until level until replacing the head off the old unit (to accept the hose connector) then rotated the compressor by hand after installed on car to release oil in the compressor
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  #4  
Old 08-23-2015, 03:19 PM
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Push button control unit.... YIKES... an 80 page section of the FSM to diagnose problems..
Are you sure the one you installed was ' good' ?
and that you hooked up all the electrical and vacuum lines correctly ?

Why did you replace the compressor ? If it suffered a ' black death' and spewed bad stuff downstream...the you may have blockage in anything you did not use a flushing liquid on ...

Actually I was referring to flushing the OLD parts.... I assume new parts are nice and clean inside...

What compressor do you have ?

Please read the AC thread in my signature..... it will help a lot...
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  #5  
Old 08-23-2015, 03:27 PM
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All new parts from Pelican....read the thread you recommended.....the CCU just had 2 electrical connectors, 16 pin each I think......except for the a/c lines I didn't touch and vacuum lines.
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  #6  
Old 08-23-2015, 03:38 PM
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Go through and answer each question you have not answered.... I am out here guessing blind at best ....
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  #8  
Old 08-23-2015, 05:18 PM
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Thanks Leathermang will do.
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  #9  
Old 08-23-2015, 05:34 PM
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It is an electrical problem if the compressor does not come on. It has nothing to do with the expansion valve. This is what I would do.

1) short the low pressure switch connector at the recv/drier. Call for A/C at the CCU, does it come on?
2) Run it for a short while as there is no freon in the system. This will confirm the CCU is working.
3) Confirm system is evacuated by pressing the low pressure schrader valve momentarily.
4) Freon/R134a should go in if system is in vacuum. If it does not then some valve in the manifold gauge may have issue.

Good luck.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

2 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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  #10  
Old 08-23-2015, 07:00 PM
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ah-kay:

I have tried grounding out the low pressure switch...the aux fan comes on, I hear the relay click but no compressor or clutch action.
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  #11  
Old 08-23-2015, 07:08 PM
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You probably jumped the high pressure switch if the aux fan comes on at low speed. Jump the 2 switches if you do not know which one, it does not hurt. You need to make sure all electrical works as expected first, compressor ( clutch ) comes on and the aux fan runs at slow speed. You may have CCU or compressor issues.

I find the low pressure switch will be 'activated' simply by charging at the low pressure port, with our without the compressor running. This has been my experience. However, you should sort out the electrical first before you start charging.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

2 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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  #12  
Old 08-23-2015, 07:15 PM
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ah-kay

I'll give another shot at jumping the switch...standby...
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  #13  
Old 08-23-2015, 07:20 PM
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I am worried that the wrong oil may be in the system... or the wrong amount...
so I was starting more basic than just trying to get it to load up refrigerant...
The lack of loading even though in a vacuum... might be due to an obstruction limiting the amount of inside capacity accessible to the installing valve location... Since we did not determine the facts concerning the need for compressor replacement...
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  #14  
Old 08-23-2015, 08:37 PM
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Quote:
Originally Posted by leathermang View Post
I am worried that the wrong oil may be in the system... or the wrong amount...
so I was starting more basic than just trying to get it to load up refrigerant...
The lack of loading even though in a vacuum... might be due to an obstruction limiting the amount of inside capacity accessible to the installing valve location... Since we did not determine the facts concerning the need for compressor replacement...
???. Nobody knows the facts except the OP.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

2 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
Reply With Quote
  #15  
Old 08-23-2015, 09:17 PM
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Join Date: Sep 2001
Location: central Texas
Posts: 17,277
Quote:
Originally Posted by ah-kay View Post
???. Nobody knows the facts except the OP.

If you read the first part of the thread you will see that I have been asking him those basic questions.
He just has not shared them yet....
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