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  #1  
Old 02-18-2010, 11:21 PM
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AC/Climate control Qestion

I've been involved in the long process of trying to figure out excactly what in the heck have the PO/PO's done to this vehicle (I'm sure i'm not the only one who has been left scrathing there heads at some of the stuff we've seen!). After doing numerous other (so far succesful) projects i've decided to tackle my non-functioning AC. I live in the S.F. east-bay area and it can get really hot over here! I just purchased a cheap set of R12 ac manifold gauges on ebay and I have basic elec. diagnostic tools. I have no experience fixing ac systems but I have done so much reading on this subject over the last few months I feel like I have a (very!) basic understanding. I pulled my PBC and re-soldered all the joints. Still no ac compressor engagement I figured it was the "Low-pressure cut-out switch" so I jumped the 2 wires still no clutch engage. I thought that was wierd?? So I gave the compressor itself a good visual inspection (I know I should've done this first!). There is no wires going to the compressor!! A little more investing as two where they are and I think I found them. A green and a brown wire were tucked underneath a bunch of other wires they both have had there terminations cut off. Can anyone confirm if these are the correct colors for the ac compressor? If so what sides do they go to?? I'm assuming there's something wrong with the compressor(Black death)?? Will it hurt anything to reconect the compressor to verify this?? I'm really looking for suggestions on haow I should proceed and diagnose the problems with my ac?? Thank you guys for your help!!

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Old 02-19-2010, 01:05 AM
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At present it seems that you only know that you have not connected 12 volts to the compressor clutch to see if it is working.... you have no evidence anything is wrong with the compressor yet...
It will not hurt to put 12 volts to the compressor clutch momentarily to see if it will engage. Since you have gauges... attach them first and see if there is ANY pressure in the system. Tell us the reading. Read the pressure at both the high and low side fittings.
Tell us what kind of refrigerant fittings your car has.
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Old 02-19-2010, 11:35 AM
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I'm going to test the pressure today. Can anyone check their compressor for the the colors of the wires? Will there be any pressure with the car or the compressor off?
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Old 02-19-2010, 12:49 PM
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There will be pressure if it is charged with refrigerant..
but it should have the same pressure on both sides... the high and low...
only if you run the compressor should it have a difference...
after sitting a while it equalizes in the system.
This is just a guess... but I think MB uses brown for ground...
At this point all you are looking for is an indication that the compressor clutch is able to respond to 12volt to engage. So that is just going to be a ' click' sound.
Then we can go forward from there.
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Old 02-19-2010, 04:20 PM
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before you do that it might be prudent to first try and turn the compressor by hand engine not running of course just to make sure the compressor is not locked up/siezed.
The wires may have been cut to prevent the serpintine belt getting burned up with a stuck compressor trying to engage.

Steve
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Old 02-19-2010, 04:34 PM
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I was only suggesting first to find if the clutch sounds like it will engage...
Then however it was activated it could be ' actualized' while the engine was running... which would mean it would be immediately noticeable that it was not turning...and could be deactivated just as fast.
it would not be prudent to activate it and close the hood and start up the engine... turning the actual compressor by hand is a safe first test. Just be sure you are looking at the center part and not the clutch mechanism. Jumping across a safety switch like the low pressure cutout has to be done very carefully to avoid possibly huge damage.
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Old 02-19-2010, 04:54 PM
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mmmmmm Diesel...
 
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I still can't turn the compressor by hand on my car. Not enough room for me to get a good grip on the thin clutch plate.

The green and brown wires sound correct. Green should have 12 volts and brown is ground. Are you getting voltage at the wires?

You can also jumper the A/C clutch to the battery, just to see if the clutch responds
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70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K
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Old 02-19-2010, 05:20 PM
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Quote:
Originally Posted by rrgrassi View Post
I still can't turn the compressor by hand on my car.
Time to renew that membership to ' Gold's Gym' ....LOL
When working on the compressor and needing to turn the actual shaft there is a tri fingered adjustable spanner with a nice handle they use...
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Old 02-20-2010, 06:02 PM
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I reconnected the cut wires to the compressor and it engaged. It ran quietly. I checked the sight glass on the drier and could barely see anything. It looked like it was splashed when the comp. kicked on and then nothing.. Then I turned off the compressor and hooked up my ac gauges (R12 "pit-bull" gauges E-bay $30). I tried to youtube and I checked this forum forever to try and determine if ur supposed to open both high/low gauges when checking pressure or separately(i probably should've just asked here, i just don't wanna be a pain in the butt!) Any way i checked it all different ways... A brownish oily liquid made its way into the sight glass on my gauge. here's the pic's of my results. I don't imagine its gonna be good.... given these results what do you guys think??
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AC/Climate control Qestion-gaugereading.jpg  
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Old 02-20-2010, 06:07 PM
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mmmmmm Diesel...
 
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Leave the guages closed to do a pressure check.

At least you know the compressor engages.

I do not think the bown color is a positive thing. Could be a bit of rust or other contamination.
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70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K
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Old 02-20-2010, 06:46 PM
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"Leave the guages closed to do a pressure check."

How would the gauges read any pressure if they are closed?
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Old 02-20-2010, 07:03 PM
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Quote:
Originally Posted by dcianfarini View Post
"Leave the guages closed to do a pressure check."

How would the gauges read any pressure if they are closed?
The valves open to the service port. The Hi and low side hoses are connected to the gauges.
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  #13  
Old 02-20-2010, 07:42 PM
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I'll take your word for it! it just seemed a little counter-intuitive at first... Any ideas on what I should do next??
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  #14  
Old 02-20-2010, 11:55 PM
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You can find a tutorial on the gauges .... they ARE counter intuitive to me...
While seeing brown inside the sight gauge is not good...

Other than that sort of pretty unusual indicator... the Factory Shop Manual cautions against putting much stock in the sight glass as an indicator.... it can sometimes give signs ( I think they mention bubbles ) which on other cars would indicate something bad but is not the case with our cars...

So go to the pressure indications for evaluation ...

But it sounds like your receiver dryer gave way or something really bad....and it might be best to just go with a flush and refill at this point in time...
Have never heard of the stuff looking brown inside the sight glass....

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