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 > Vintage Mercedes Forum

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 04-22-2006, 08:12 PM
Milt
 
Join Date: Jul 2002
Location: N.W. Arkansas
Posts: 172
Air Condition Pressures.

I am comparing job no 83-502 in the c.d. ( air conditioning diagram) with the description of the A. C. circuit on a can of oil charge and they don 't seem to match. Intuitively I think the the C.D. is opposite of what I think it should be and wrong. I think the diagram on the can is right. The can says the evaporator part of the circuit is the low pressure side and the condenser part of the circuit is the high pressure side. This seems to be the opposite of diagram 83-502. Could someone tell me whether I am right or wrong, i.e., is the c.d. diagram wrong. Milt.

__________________
Milterino
76 450 S.E.L.
Reply With Quote
  #2  
Old 04-22-2006, 11:03 PM
Registered User
 
Join Date: Mar 2006
Location: new mexico
Posts: 70
i haven't seen the c.d. but the condensor side is the high side.
Reply With Quote
  #3  
Old 04-23-2006, 12:56 AM
Motorhead's Avatar
Registered User
 
Join Date: Dec 2002
Location: Ca.
Posts: 976
On every car A/C system I have worked on, the HIGH pressure side or DISCHARGE has the smaller diameter hose or hard line. The LOW side is the larger diameter. Just that question is why on later cars they used two different sized fittings to hook up the gauges. You want about 30-35psi on the low side with the engine at high idle (about 1200 to 1500rpm). Don't over charge... and don't put in too much oil as it can cut efficiency.
__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.
Reply With Quote
  #4  
Old 04-23-2006, 11:32 AM
Milt
 
Join Date: Jul 2002
Location: N.W. Arkansas
Posts: 172
Air Condition Pressures

Thanks for your replies. Motorhead, you mention the discharge side, I assume that you mean the discharge side of the compressor. Is that correct? I am assuming the flow of the refrigerant is from the evaporator thru the compressor to the condenser to the dehydrator to the expansion valve and to the evaporator again.
Someone told me you can clean the refrigerating circuit by opening the valve on the high pressure side and running R134 into the valve on the low pressure side. Is this a reasonable assumption? Thanks again for you advice. Milt.
__________________
Milterino
76 450 S.E.L.
Reply With Quote
  #5  
Old 04-23-2006, 11:38 AM
Tomguy's Avatar
Vintage Moderator
 
Join Date: Aug 2002
Location: near Scranton, PA
Posts: 5,407
Trying that will leak old R12 into the atmosphere (illegal) and the chances you get 100% of it out without a proper a/c vacuum pump is 0%. Also, R12 oil is incompatible with R134. If you want to convert your system the easy way, at LEAST make sure someone removes ALL of your old R12 and oil completely.

Better than converting to R134 is topping off with Freeze-12 or actual R12.
__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k
Reply With Quote
  #6  
Old 04-23-2006, 12:02 PM
Milt
 
Join Date: Jul 2002
Location: N.W. Arkansas
Posts: 172
Air Condition Pressures

Tomguy, It was converted to R134 about 3 years ago. About 6 months ago a 2X4 cut the high pressure (small diameter) line from the dehydrator to the expansion valve and I have just now started to do anything about it so I assume the athmosphere has gotten in the circuit. My plan was to run a can of r134 thru it and then close the circuit and add a small can of R134a ester oil charge (2 oz) and recharge it with r 134. Any comments welcome. Milt.
__________________
Milterino
76 450 S.E.L.
Reply With Quote
  #7  
Old 04-23-2006, 02:27 PM
Motorhead's Avatar
Registered User
 
Join Date: Dec 2002
Location: Ca.
Posts: 976
Milterino, Yes the discharge is from the compressor high pressure side. Chris
__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.
Reply With Quote
  #8  
Old 04-23-2006, 02:43 PM
Tomguy's Avatar
Vintage Moderator
 
Join Date: Aug 2002
Location: near Scranton, PA
Posts: 5,407
I wouldnt do it because moisture supposedly combines with the oils in the system at the high pressures to form acid, so ANY air in the system will yield an amount of moisture (once it's compressed). I'm not an A/C tech but I wouldnt risk my compressor or other components.
__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k
Reply With Quote
  #9  
Old 04-23-2006, 02:50 PM
Motorhead's Avatar
Registered User
 
Join Date: Dec 2002
Location: Ca.
Posts: 976
I second Tomguy..... You need to have the system evacuated to help remove moisture and I would also replace your receiver drier. If replacing the receiver dryer, you will need some more oil.
__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.
Reply With Quote
  #10  
Old 04-26-2006, 11:54 PM
Milt
 
Join Date: Jul 2002
Location: N.W. Arkansas
Posts: 172
Air Condition Pressures

Does anybody know what the pressure should be in the high pressure side of the air conditioning system? Milt.
__________________
Milterino
76 450 S.E.L.
Reply With Quote
  #11  
Old 04-29-2006, 10:49 AM
Registered User
 
Join Date: Oct 2005
Posts: 4,263
Quote:
Originally Posted by milterino
Does anybody know what the pressure should be in the high pressure side of the air conditioning system? Milt.
The pressure depends on a whole host of variables. Get out your thermometers and hygrometer and look at the AC chart in the manual, and assume that you can exceed the R12 high-side value by a bit, if necessary. You should need about 85% of the proper R12 charge by weight.

You don't want the low-side to be too high, as this will increase the evaporator temperature. The pressure switch should have been changed to also have a high-pressure cutout at about 30 bar. If it's not been changed, it needs to be.

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 12:08 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page