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 07-01-2011, 11:23 PM
Registered User
 
Join Date: Feb 2008
Posts: 59
1983 300CD AC Vent Temperature

I just had a completely new AC put on my 83 300CD (new compressor, expansion valve, & drier). Got the car back today. I am disappointed in the center vent temp which is 52F with 90F outside temp. This is with the setting on low as possible and the car on the interstate at 70MPH for 30 minutes. Everything seems normal with the aux. fan coming on at idle. The MB mechanic who did the job has 50 pressure on the low side at idle. I forget the high pressure, but he said it was fine when I asked him to recheck. The low pressure seems high to me, but he said this is what is correct for 90F outside. My question is if this pressure is ok, why isn't the temp out the center vent lower? Would lower pressure on the low side, give a lower temp out the center vent? He used 134. Any insight would be appreciated.

Richard

Reply With Quote
  #2  
Old 07-01-2011, 11:29 PM
pelon's Avatar
Up through the hawespipe.
 
Join Date: Oct 2008
Location: Valencia, NM
Posts: 218
Take it back

Have him vacuum it out and install R-12 like it was built for.
__________________
1985 300SD
1998 Jetta TDI
Previous: lots of diesel VW's, MB's, KW's, Pete, Freightliner


Walking isn't a lost art: one must, by some means, get to the garage.
Reply With Quote
  #3  
Old 07-01-2011, 11:29 PM
Registered User
 
Join Date: May 2004
Location: Natchez MS and Dallas TX
Posts: 355
FWIW I had the same new parts plus a parallel condenser and only get 60 degrees on my 85 300SD.
__________________
85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K
Reply With Quote
  #4  
Old 07-02-2011, 12:25 AM
Registered User
 
Join Date: Sep 2004
Posts: 8,956
Quote:
Originally Posted by xke190sl View Post
He used 134. Any insight would be appreciated.
R-134a works great in a W123. In April and October.
Reply With Quote
  #5  
Old 07-02-2011, 01:41 PM
Yak Yak is offline
Registered User
 
Join Date: Aug 2009
Location: San Antonio, TX
Posts: 1,711
134a is not the best choice for the W123. If you can find R-12 and a tech who'll install it, that would work better. However, if you've got PAG oil in the system now (for 134) you'd need the system flushed to swap back to R-12 with mineral oil (for best cooling and lube on the R4 compressor. If you put ester oil (not as good lube, but compatible with both 12 and 134a), then a refrigerant swap could be easier, but you've now got the wrong fittings.

50 psi may be okay at idle, or you may be a bit overcharged (there's an estimated ratio of about 0.8 to 1.0 for 134a to R-12), or at idle in the shop the temps may be higher. 134a pressures are more finicky to measure based on temps. See the attached chart. http://www.ackits.com/aacf/ptchart.cfm
Reply With Quote
  #6  
Old 07-02-2011, 01:49 PM
JHZR2's Avatar
Registered User
 
Join Date: Jan 2002
Location: New Jersey
Posts: 4,908
Yeah, Id run R12. Dont think there is as huge a cost delta anymore... R134a is going to go up in cost bigtime...
__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
Reply With Quote
  #7  
Old 07-02-2011, 03:23 PM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,281
I bought a couple of cans of R134a at OReilly's and paid $18 per 12 oz... I almost fell over...it was about $6 the last time..
Reply With Quote
  #8  
Old 07-02-2011, 05:17 PM
Yak Yak is offline
Registered User
 
Join Date: Aug 2009
Location: San Antonio, TX
Posts: 1,711
Quote:
Originally Posted by xke190sl View Post
I just had a completely new AC put on my 83 300CD (new compressor, expansion valve, & drier). Got the car back today. I am disappointed in the center vent temp which is 52F with 90F outside temp. This is with the setting on low as possible and the car on the interstate at 70MPH for 30 minutes. Everything seems normal with the aux. fan coming on at idle. The MB mechanic who did the job has 50 pressure on the low side at idle. I forget the high pressure, but he said it was fine when I asked him to recheck. The low pressure seems high to me, but he said this is what is correct for 90F outside. My question is if this pressure is ok, why isn't the temp out the center vent lower? Would lower pressure on the low side, give a lower temp out the center vent? He used 134. Any insight would be appreciated.

Richard
Having had a bit of trouble convincing an A/C tech that I wanted to know both high and low pressures, I'd be a bit skeptical of the "it's fine" assessment.

The location of the high side port and the possibility that it's still an R-12 port in an otherwise 134a system would cause me to investigate a bit more. My tech initially said "there's no need to hook up to that side..." since the high side port is under the car. He did it when I pressed the issue and so he could fill the system faster after it was evacuated.

Double check the high side on the bottom near the alternator. If it's a small metal cap, that's probably still an R-12. If it's a larger red plastic cap, that's probably a 134a cap. If you paid to have the system rebuilt and filled with 134a, they should have done the job completely and you should be able to get high side numbers.
Reply With Quote
  #9  
Old 07-02-2011, 05:35 PM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,281
[QUOTE=Yak;2745591]Having had a bit of trouble convincing an A/C tech that I wanted to know both high and low pressures.....[QUOTE]

That is amazing... Do you still use him ? Makes him sound ' slippery ' even if he is not...
Reply With Quote
  #10  
Old 07-03-2011, 11:19 AM
Registered User
 
Join Date: Apr 2006
Location: South Florida
Posts: 467
Make sure the flap that lets outside air in is completely closed (on the SD it's behind the glove compartment. You can see it by popping out the oblong black plastic cap that covers a peep hole in the top left back inside of the glove compartment.)

If it's open (due to vacuum leak in hose, pod, and/or failed switch) you can prop it shut by (carefully-don't damage insulation on the flap) by wedging a 3.0" to 3.5" long item (clothes pin, pencil etc.) between the back of glove compartment and the flap.

Should give you a 10F drop.
__________________
'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.
Reply With Quote
  #11  
Old 07-03-2011, 02:25 PM
Yak Yak is offline
Registered User
 
Join Date: Aug 2009
Location: San Antonio, TX
Posts: 1,711
[QUOTE=leathermang;2745603][QUOTE=Yak;2745591]Having had a bit of trouble convincing an A/C tech that I wanted to know both high and low pressures.....
Quote:

That is amazing... Do you still use him ? Makes him sound ' slippery ' even if he is not...
Once he got started he did a thorough job. Since the A/C equipment was in a bay that didn't have a jack he was probably looking to take the route that meant the least amount of jockeying things around. The initial request was for evacuation and charge. Once he saw it was an R-12 system, converted to 134a, after an overhaul with the addition of new components, he was a little less laissez-faire about it.

He eventually did the full tests, including putting the high flow fan in front of the car to simulate on-the-road conditions to supplement aux fan air flow.
Reply With Quote
  #12  
Old 07-03-2011, 04:05 PM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,281
Yak, Well, glad to know he ' saw the light' ... with you in charge it got done right...

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 02:24 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2023, 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