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 > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 08-03-2004, 11:57 AM
Registered User
 
Join Date: Nov 2003
Location: St. Louis, MO
Posts: 16
'87 300E A/C problem

Hi all! My A/C on my '87 300E quit working. Evacuated system to -25 inch @ ambient temp of about 93F with 70% humidity. Held for 30 minutes. I charged it to 35psi with R12. Clutch engaged. Pressure readings: low side 35psi, high side 35psi. It's obviously not pumping. Is it "Black Death" or could something be clogged enough to cause this? There is a noticable leak behind the expansion valve (lines are wet with oil). I am sure the evaporator needs to be changed. I took the dryer off and blew compressed air through it with a white cloth to catch anything that may come out. Just a little oil, nothing that looked like teflon flakes (unless they look like oil or powdered graphite). Where should I look next? Thanks in advance.

Reply With Quote
  #2  
Old 08-03-2004, 12:54 PM
Moderator
 
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
R-12 has a pressure temp relationship that will have it at over 100psi on a summer day. If your system has only 35psi on the high side, you have almost no refrigerant in the system.

As to your procedure for evacuation. Unless you are on the top of Everest on a 100deg day, you are not doing the job with only 25in of vacuum. The concept you are trying to achieve is that you are wishing to boil the water at ambient temp. This gets easier at altitude but at sea level and a 90 degree day thevacuum that must be pulled to make the boiling point drop below 90 degrees is closer to zero psi absolute than standard gauges will tell you. one needs a micron gauge to view the actual level necessary.

The concept is to lower the pressure to the point moisure is boiled at ambient temp and then time is needed to finish the boiling.
__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
Reply With Quote
  #3  
Old 08-03-2004, 01:38 PM
Registered User
 
Join Date: Nov 2003
Location: St. Louis, MO
Posts: 16
Thanks for the reply. I realize that at 90F I would need to pull about 28.5 inches of vacuum (about 35,000 microns) to boil. With the leak in the system, it's not possible. My main question is when the clutch engages, shouldn't the high side go up and the low side go down? I have no difference in the two sides with the compressor running. Even with an undercharge, shouldn't it move refrigerant?
Reply With Quote
  #4  
Old 08-03-2004, 02:05 PM
Moderator
 
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Yes, I'm guessing you aren't getting the schrader valve open to your gauge. Put more refrigerant in and try again. Be sure the center of the clutch hub is spinning. The hub is rubber and they do tear allowing the otherside to spin with the actual compressor not.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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 01:27 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, 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