Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 04-25-2018, 12:30 PM
Registered User
 
Join Date: Feb 2016
Location: North New Jersey
Posts: 390
evaluating an AC compressor when system is currently discharged

The compressor on my car (82 300D) is currently hooked up via the belt, not seized to my knowledge, and not original to the vehicle. My system is still r12.

I'm about to start an attempt to revive my AC. Before I pour incredible amounts of money into it or tearing apart the whole system and dash - which i'm unwilling to do - I want to start with receiver dryer, vacuum the system, attempt to check for major leaks, new oil and some r12 I have. Perhaps just swap in a new expansion valve too. But obviously all of this is pointless if my compressor isn't coming back to life. How can I evaluate the basic operational condition of the compressor? Since my system is not charge, its obviously not going to kick on.. or should it?

Also - is this service port in this photo my high side or my low side? https://photos.app.goo.gl/CihVmHgBXLgemLeW2
__________________
Andrew
Montclair, NJ
--------------
1982 300D Turbo
117k
Petrol Blue/Green

Last edited by kuene; 04-25-2018 at 12:52 PM.
Reply With Quote
  #2  
Old 04-25-2018, 01:11 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,548
Quote:
Originally Posted by kuene View Post
Also - is this service port in this photo my high side or my low side?
Low.
__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
Reply With Quote
  #3  
Old 04-25-2018, 01:12 PM
ILUVMILS's Avatar
Senior Member
 
Join Date: Sep 2002
Posts: 2,522
You can jump the low pressure switch and the compressor should come on. Don't run it for more than a few seconds though.........
Reply With Quote
  #4  
Old 04-25-2018, 01:57 PM
Registered User
 
Join Date: Jan 2018
Posts: 236
See if the center portion of the pulley can be turned by hand. If so, compressor is not locked.
Reply With Quote
  #5  
Old 04-25-2018, 02:02 PM
Registered User
 
Join Date: Jan 2012
Posts: 6,322
Does this have the R4 ( GM ) compressor? I'd pull the discharge hose and look for metal / gray coating ( aluminum wear ) in the compressor discharge port as both are a sign of compressor issues.

With the engine off, turn the compressor clutch by hand, it should rotate pretty smoothly. ( not the belt driven pulley, the face of the clutch )

A failed compressor is the least of your concerns if you are unwilling to pull the dash for a evaporator change. The next step is to pressurize the system with nitrogen or even R134 since it is handy and R12 is $$$ . See if it holds pressure overnight, of not, isolate components with plugs to narrow things down. With R134 you can use a freon sniffer to locate an actual leak.

When pressurizing with R134 you do not need to run the compressor or fully change the system. Just connect the hose, open the can and let the gas flow. When pressure has stabilized, disconnect the can.
Reply With Quote
  #6  
Old 04-25-2018, 02:20 PM
Registered User
 
Join Date: Feb 2016
Location: North New Jersey
Posts: 390
Thanks for tips. I disagree about what is and isnít the lest of my concerns. The compressor is one of the components I can easily get access to. If itís crapped out, then my AC quest ends. If it works, then I move on to next step. Iím not assuming my evaporator is fine, but Iím not going to start this whole thing by tearing apart my dash. AC will be a nice to have.

Is it safe to put r134 in m system to check for leaks under pressure when I am definitely not converting it from r12? It wonít harm the seals or other components?
Reply With Quote
  #7  
Old 04-25-2018, 04:14 PM
Diseasel300's Avatar
Registered User
 
Join Date: May 2016
Location: Texas Hill Country
Posts: 4,103
R134a won't harm the seals or anything else in the system. The W123 and W126 aren't known for having a lot of problems with the evaporator. The later 124's and 140s are much more common evaporator replacement candidates.

If you're going to have the system open already, do the job right and do it once. Check the discharge side of the compressor for metal as mentioned above and replace *EVERY* o-ring you can get to. They're your most common source of leaks.

Be aware that modern expansion valves are designed for R134a and have a smaller orifice size. Running R12 on an R134a expansion valve can result in poor cooling. Unless the system has been open to the air for a period of time or had the compressor grenade and send shrapnel through the hoses, the expansion valve is probably ok.
__________________
'11 Honda Accord EX - "The Daily" 64K
'83 500SL Euro - "The Money Pit" 116K
'86 300SDL - "The Diseasel" 186K
The Diseasel Thread - Everything You Didn't Know You Wanted To Know
Reply With Quote
  #8  
Old 04-25-2018, 11:28 PM
Registered User
 
Join Date: Mar 2016
Location: HouTex
Posts: 110
Do you have A.C. Tools?
I would pull a vacuume on the system and see how long it stays tight. Next if it has remained sealed and nothing is oily you could try giving it some 134a, jump compressor out and see how it sounds and works.

From there you can decide if you want to go ahead with full 134a conversion, changing O rings etc or dig deep into the savings account for some r12. I like r12 but would not charge it with such unless I knew all was tight.

Sometimes when older dormant systems are brought back online they will find any weak points in the system within a week or so of using them.
__________________
1995 E300 (W124)
1999 ML430 (w163)
2011 GL350 (x164)
2016 Sprinter 144" 4X4 lowtop (906)
Reply With Quote
  #9  
Old 04-26-2018, 12:10 AM
ROLLGUY's Avatar
ROLLGUY
 
Join Date: Oct 2007
Posts: 5,909
Guaranteed you have a leak, and that is why the system is discharged. Most likely it is an Oring or compressor seal. It could also be a hose. It would be best to find the leak before proceeding. Pulling a vacuum will NOT help in any way to find a leak. Pressurizing with nitrogen is the best way. Spray a mixture of soap and water on all the fittings and hoses. The problem with the R4 is that it has no oil sump. When the refrigerant leaks out, the oil goes with it. If you find a leak and then fix it, you won't know how much, or if any oil is still in the system. Guessing at how much oil is remaining is just that- a guess. Too little oil, and the compressor will eat itself up. Too much oil, and the cooling efficiency will suffer. The BEST thing to do is flush the entire system except the compressor, and start over. While flushing, if you see anything that looks like metal, or the oil is black or dirty, the compressor should be replaced. Once everything is back together (the drier is the last component connected), check for leaks again.
Of course I would suggest going with a Sanden retrofit. You will be money ahead in the long run. Even if your R4 has life left in it, my bet is that it is not a lot of life. A short lived R4 is a common theme in these cars........Rich
Reply With Quote
  #10  
Old 04-26-2018, 10:31 AM
Registered User
 
Join Date: Feb 2016
Location: North New Jersey
Posts: 390
Thanks for all this great info.

I do have gauges, vacuum pump, new orings, and in fact cans of r12 and a can of r12/oil.

Iím not going to just throw r12 into the system and risk losing it and of course being a jerk with the atmosphere.

I donít think the system has been fully open to air - in fact when I just touch the shrader valve a little pressure still release - perhaps that is meaningless.

I think Iíll evaluate the compressor and post some pics of it next.
Reply With Quote
  #11  
Old 04-26-2018, 11:39 AM
Registered User
 
Join Date: Oct 2012
Posts: 4,414
The small amount of pressure remaining is a better situation then none at all. At least in my opinion. Defeat the low pressure cut out for a second or so to see if the compressor runs as well.
Reply With Quote
  #12  
Old 04-27-2018, 01:12 AM
Registered User
 
Join Date: Jan 2018
Posts: 236
Guy told me the AC didn't work in my W124 when I bought it. Same as yours, it had a little pressure in the system. Read 20psi static when I put a gauge on it. Charged it up and it works perfectly. I'm sure it probably has a slow leak, but the compressor was free and it still had 134 in it. I vacced it down and recharged it in Feb. Freeze you out right now with temps in the 80s.
Reply With Quote
  #13  
Old 04-27-2018, 11:30 PM
ROLLGUY's Avatar
ROLLGUY
 
Join Date: Oct 2007
Posts: 5,909
Quote:
Originally Posted by MCallahan View Post
Guy told me the AC didn't work in my W124 when I bought it. Same as yours, it had a little pressure in the system. Read 20psi static when I put a gauge on it. Charged it up and it works perfectly. I'm sure it probably has a slow leak, but the compressor was free and it still had 134 in it. I vacced it down and recharged it in Feb. Freeze you out right now with temps in the 80s.
Your W124 probably has the Denso compressor, and is much better at keeping sealed than the R4. The Denso is similar design to a Sanden.Having 30+ year old hoses doesn't help either. I would not gamble with an R4 or old hoses, hoping it will keep the R12 in the system. It is just too costly.
Reply With Quote
  #14  
Old 04-28-2018, 12:55 PM
Registered User
 
Join Date: Jan 2018
Posts: 236
Running 134 in this one, so not too worried. Hoses seem fine. Will take my chances until proved otherwise.
Reply With Quote
  #15  
Old 04-28-2018, 01:08 PM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,180
NEVER CHECK FOR LEAKS WITH VACUUM...

ALWAYS USE PRESSURE FOR 24 OR MORE HOURS.
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 12:43 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page