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 08-13-2010, 07:48 AM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Low Side Pressure Recommendations

On my 91 300D, AC was weak due to slow leak and aux fans weren't coming on at all. I didn't have a proper set of gauges (my next purchase), but I did have a charging gun with a low side gauge. Reading was about 37 psi at 80F or so.

The charging gun came with the pressure recommendations at the end of this post. So I added refrigerant until pressure was about 45 (took about 10oz.).

AC is cold, fans are coming on. But my concern is that, by simply using these generic recommendations, I may have overcharged the system (based on what a couple of knowledgeable MB folks have told me).

Thoughts?

Thanks for your continued help as I continue along the learning curve.



Ambient Temp Pressure

65 25-35

70 35-40

75 35-45

80 40-50

85 45-55

90 45-55

95 50-55

100 50-55

105 50-55

110 50-55

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife
Reply With Quote
  #2  
Old 08-13-2010, 08:11 AM
LarryBible
Guest
 
Posts: n/a
I would NEVER recommend charging based solely on low side pressure. Buy, beg, or borrow a manifold gauge set so you're not trying to fight with one arm tied behind your back.
Reply With Quote
  #3  
Old 08-13-2010, 08:23 AM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Quote:
Originally Posted by LarryBible View Post
I would NEVER recommend charging based solely on low side pressure. Buy, beg, or borrow a manifold gauge set so you're not trying to fight with one arm tied behind your back.
Buying a set this weekend. Do I use pressure recommendations that come with kit, or is there something more specific for my car?
__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife
Reply With Quote
  #4  
Old 08-13-2010, 08:55 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,835
ahh. now I understand, your PM's didn't have all this info.
yes, I'd say you are overcharged. heed the warnings I gave you in the PM's and larry's word is golden.
I think now you need to go to a shop and get some 134 removed from the system.
like I told you in the PM's it's just too difficult to explain all the variables to a DIY without any tools. the slow charging procedure I outlined will get you in the ballpark, but please don't pay attention to the charging chart. showing you low pressures based on outside ambient leaves out a huge amount of info for getting your system right.
__________________
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
  #5  
Old 08-15-2010, 10:16 PM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Quote:
Originally Posted by vstech View Post
ahh. now I understand, your PM's didn't have all this info.
yes, I'd say you are overcharged. heed the warnings I gave you in the PM's and larry's word is golden.
I think now you need to go to a shop and get some 134 removed from the system.
like I told you in the PM's it's just too difficult to explain all the variables to a DIY without any tools. the slow charging procedure I outlined will get you in the ballpark, but please don't pay attention to the charging chart. showing you low pressures based on outside ambient leaves out a huge amount of info for getting your system right.
I should add that the reading I took was with engine at idle. So low side pressure is less with engine at 1500 rpm or so. As to how much less, I will need to enlist the support of my "assistant" (aka wife). Anyway, perhaps my initial report was skewed high....
__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife
Reply With Quote
  #6  
Old 08-15-2010, 10:31 PM
whunter's Avatar
Moderator
 
Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,416
FREE Generic A/C training material for beginners:

Quote:
Originally Posted by shertex View Post
I should add that the reading I took was with engine at idle. So low side pressure is less with engine at 1500 rpm or so. As to how much less, I will need to enlist the support of my "assistant" (aka wife). Anyway, perhaps my initial report was skewed high....
Climate Control:
http://www.peachparts.com/shopforum/showthread.php?t=142408






Have a great day
Attached Thumbnails
Low Side Pressure Recommendations-r134a-pressure-vs-temp-chart.jpg   Low Side Pressure Recommendations-r12_r134a_pressure-temp_x6fhgt5465.jpg  

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Last edited by whunter; 08-15-2010 at 11:08 PM.
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 07:35 AM.


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