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 08-21-2013, 09:15 AM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
AC Charging Questions

On the 95 E300D I'm selling, the AC doesn't work. However, I have confirmed that the compressor engages when the low-pressured cut-off switch is jumpered. So that's a good sign.

I tried to add some refrigerant to see if I could get the compressor to engage. But, after almost a full 12 oz. can, it wouldn't. I saw a static low side pressure of about 70....but I gather that's a meaningless number.

Should I try to add another can? Or is that risky?

I know that the proper way to see what's going on is to evacuate and recharge the system. However, I'm not willing to spend money on getting the AC diagnosed....I will leave that to the new owner.

Thanks.

__________________
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 08-21-2013, 09:48 AM
Registered User
 
Join Date: Aug 2001
Location: Milford, DE
Posts: 1,558
The 70 psi static reading isn't meaningless.... it tells me the ambient temp when you took the reading was somewhere around 70F.

The safety cut-out switch doesn't activate until the system pressure gets very low, like around 20 psi. Since you can jumper it and get it to engage it would appear at least your 1st issue is in the compressor control circuit or a bad safety switch.

Another can of R134 won't help - 70 PSI is plenty high enough to energize the safety cut-out circuit.
__________________
98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)
Reply With Quote
  #3  
Old 08-21-2013, 10:58 AM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,038
Maybe the Klima relay is preventing it from engaging somehow? Can you get a gauge on the high side and see what it is doing?
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
Reply With Quote
  #4  
Old 08-21-2013, 01:27 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,841
It could be a bad low pressure switch. Unfortunately you have to evacuate the system to replace it. On a car with over 300K miles, I'd be tempted to jump the low pressure switch, with full disclosure to the buyer of course, and enjoy the summer. I've never heard of a high pressure failure in these cars though you might have tilted the table with the extra 12oz Cooling capability will be notably diminished before the low pressure trigger so you'd know to do something about it if it fails in the summer.

Sixto
87 300D
Reply With Quote
  #5  
Old 08-21-2013, 07:56 PM
engatwork's Avatar
Registered User
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,648
Try another Klima relay.
__________________
Jim
Reply With Quote
  #6  
Old 08-21-2013, 08:39 PM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Quote:
Originally Posted by sixto View Post
It could be a bad low pressure switch. Unfortunately you have to evacuate the system to replace it. On a car with over 300K miles, I'd be tempted to jump the low pressure switch, with full disclosure to the buyer of course, and enjoy the summer. I've never heard of a high pressure failure in these cars though you might have tilted the table with the extra 12oz Cooling capability will be notably diminished before the low pressure trigger so you'd know to do something about it if it fails in the summer.

Sixto
87 300D
That's an interesting idea.
__________________
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
  #7  
Old 08-21-2013, 08:40 PM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Quote:
Originally Posted by engatwork View Post
Try another Klima relay.
That was my thought originally....kinda pricey though. I wish I had a known good one I could try. That's why I love having the 91 and the 92....I can diagnose by swapping parts.
__________________
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
  #8  
Old 08-21-2013, 09:33 PM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Quote:
Originally Posted by sixto View Post
It could be a bad low pressure switch. Unfortunately you have to evacuate the system to replace it. On a car with over 300K miles, I'd be tempted to jump the low pressure switch, with full disclosure to the buyer of course, and enjoy the summer. I've never heard of a high pressure failure in these cars though you might have tilted the table with the extra 12oz Cooling capability will be notably diminished before the low pressure trigger so you'd know to do something about it if it fails in the summer.

Sixto
87 300D
Sixto, in a situation like that, if the compressor fails due to low refrigerant (and a jumped low pressure switch), does the clutch disengage or does it stay engaged and thereby mess up the belt?
__________________
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
  #9  
Old 08-21-2013, 10:49 PM
rrgrassi's Avatar
mmmmmm Diesel...
 
Join Date: Jun 2006
Location: Royse City Tx
Posts: 5,177
If the compressor disengages, no belt issues. If the compressor stays engaged, like if the low pressure switch is jumped, and the compressor locks up, well belt damage can occur.

That is why I like the old V belts. You can cut the compressor belt and not worry about the water pump, alternator, etc.
__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K
Reply With Quote
  #10  
Old 08-22-2013, 05:53 AM
engatwork's Avatar
Registered User
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,648
Quote:
If the compressor disengages, no belt issues. If the compressor stays engaged, like if the low pressure switch is jumped, and the compressor locks up, well belt damage can occur.
Not true on the 95. The system looks at the speed of the compressor and compares it to the speed of the engine and disengages the compressor if there is a speed difference.

Try another over voltage protection relay (this is what I meant to say in reference to the Klima relay). They should be interchangeable between the 95 and 93.
__________________
Jim
Reply With Quote
  #11  
Old 08-22-2013, 07:22 AM
Registered User
 
Join Date: Jul 2004
Location: Barrington, RI
Posts: 5,874
Weirdest thing....woke up, armed with gauge and charging gun, read zero static pressure, charged the system, and it blows ICE COLD. Must be losing my mind.

So, we'll see how it goes. Low pressure cut-off appears to be fine though.
__________________
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
  #12  
Old 08-22-2013, 09:04 PM
Equestrian's Avatar
All Smoke No Spool
 
Join Date: Mar 2013
Location: Orange Co, NC
Posts: 131
Ha it healed when it was afraid of going under the knife. Seems to me that sometimes the systems on cars need 24 hours to settle for the refrigerant to circulate and equalize. Odd

__________________
1991 300d 2.5 Turbo OM602
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 09:59 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