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 07-07-2011, 03:27 AM
Registered User
 
Join Date: May 2008
Location: Bellevue, WA
Posts: 36
W124 a/c woes!

Hi all,

So I got my W124 ('94 E420) out of storage recently, and the a/c has been acting up. Most of the time it works great--with the temperature dial turned to maximum the car freezes me out most of the time. Sometimes, however (usually after the car and the a/c have been on a while) the a/c just cuts off--the blower blows, but the air temperature is the same as if I'd hit the EC switch. If I leave the car off for a few hours though, it works as normal. Does anyone have any idea what could be wrong?

Thanks!

__________________
2002 BMW 330Ci, Benzless at the moment.

Past: 1994 E420, various W123 240D rustbuckets
Reply With Quote
  #2  
Old 07-07-2011, 04:43 AM
Registered User
 
Join Date: May 2007
Location: Arizona
Posts: 757
I would start with the poly-v belt. If it slips even slightly, it may cause the a/c clutch to lock out. I don't know if it's supposed to reset automatically after this, but it has been my experience that the a/c will usually not work until you turn the engine off and restart it. If you have a code reader, you may see a DTC code 7 (poly-v belt slips) on the base module (socket 8). If you haven't changed the belt in a while, it may be a cheap fix.

Also, if you are in a really hot climate (like here in Arizona), the a/c pressure may exceed the limit and prevent the clutch from engaging. This has happened to me a few times in the hot summer where I have parked the car with ambient temperatures of 113 F and the under-hood temperature must have been incredibly high.

Also, I was told by a tech once that under really high temperatures, the pressure in the system can be so high--even with the engine off--that when you go to start the engine and engage the compressor it takes a lot of force just to initially get the compressor turning and it could cause the belt to slip and lock out.
__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles
Reply With Quote
  #3  
Old 07-07-2011, 07:12 AM
engatwork's Avatar
busy
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,643
Quote:
Also, if you are in a really hot climate (like here in Arizona),
In Switzerland?

lol

Slipping belt makes sense and it is easy to inspect the belt.
__________________
Jim
Reply With Quote
  #4  
Old 07-07-2011, 09:42 AM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,277
I am going to go with a more basic guess...
Your throttle suctioning mechanism... sometimes the Txvalve...but in more complicated systems ( than my type One ) it may have other components...
is not cutting off the cooling of the evaporator at a high enough temperature... thus below freezing fins on the evaporator are freezing the moisture in the air on the fins.... and cutting off the cold air... until you leave it to melt off and start over....
Reply With Quote
  #5  
Old 07-07-2011, 03:43 PM
Registered User
 
Join Date: May 2008
Location: Bellevue, WA
Posts: 36
Quote:
Originally Posted by emerydc8 View Post
I would start with the poly-v belt. If it slips even slightly, it may cause the a/c clutch to lock out. I don't know if it's supposed to reset automatically after this, but it has been my experience that the a/c will usually not work until you turn the engine off and restart it. If you have a code reader, you may see a DTC code 7 (poly-v belt slips) on the base module (socket 8). If you haven't changed the belt in a while, it may be a cheap fix.

Also, if you are in a really hot climate (like here in Arizona), the a/c pressure may exceed the limit and prevent the clutch from engaging. This has happened to me a few times in the hot summer where I have parked the car with ambient temperatures of 113 F and the under-hood temperature must have been incredibly high.

Also, I was told by a tech once that under really high temperatures, the pressure in the system can be so high--even with the engine off--that when you go to start the engine and engage the compressor it takes a lot of force just to initially get the compressor turning and it could cause the belt to slip and lock out.
Hmm.. the v-belt was replaced last year and seems to have sufficient tension. Also, if I leave the car off for just a few minutes (eg getting gas) the compressor doesn't kick back on (but it will if the car has been off for a few hours). It's been pretty warm here in Columbus, OH (not Geneva! oops, updated that).

Quote:
Originally Posted by leathermang View Post
I am going to go with a more basic guess...
Your throttle suctioning mechanism... sometimes the Txvalve...but in more complicated systems ( than my type One ) it may have other components...
is not cutting off the cooling of the evaporator at a high enough temperature... thus below freezing fins on the evaporator are freezing the moisture in the air on the fins.... and cutting off the cold air... until you leave it to melt off and start over....
It definitely behaves like it's freezing over and then working again when it's thawing out. Where could I find the throttle sucking mechanism/txvalve?

Thanks!
__________________
2002 BMW 330Ci, Benzless at the moment.

Past: 1994 E420, various W123 240D rustbuckets
Reply With Quote
  #6  
Old 07-07-2011, 04:17 PM
engatwork's Avatar
busy
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,643
Can you provide us with a temperature reading out of the vents on the dash when it is blowing cold?
__________________
Jim
Reply With Quote
  #7  
Old 07-07-2011, 05:08 PM
Registered User
 
Join Date: May 2008
Location: Bellevue, WA
Posts: 36
Quote:
Originally Posted by engatwork View Post
Can you provide us with a temperature reading out of the vents on the dash when it is blowing cold?
Haven't checked recently but last time I did it was 42 F.
__________________
2002 BMW 330Ci, Benzless at the moment.

Past: 1994 E420, various W123 240D rustbuckets
Reply With Quote
  #8  
Old 07-07-2011, 05:48 PM
engatwork's Avatar
busy
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,643
Sounds about right.
__________________
Jim
Reply With Quote
  #9  
Old 07-07-2011, 06:56 PM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,277
I only have knowledge of type one AC's.... the simplest MB AC...notice my signature...

Someone with your kind of car..
or a FSM of your type of car will have to speak up....

You would have had more help if you had posted this to the Diesel forum..... More AC guys with later models over there...
Reply With Quote
  #10  
Old 07-07-2011, 07:22 PM
engatwork's Avatar
busy
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,643
If you are driving the car and it quits then you turn it off and crank it back up does it come on? With the engine off try spinning the "inside" portion of the compressor pulley to see how easy it is to turn.
__________________
Jim
Reply With Quote
  #11  
Old 07-07-2011, 08:34 PM
Registered User
 
Join Date: May 2008
Location: Bellevue, WA
Posts: 36
Quote:
Originally Posted by engatwork View Post
If you are driving the car and it quits then you turn it off and crank it back up does it come on? With the engine off try spinning the "inside" portion of the compressor pulley to see how easy it is to turn.
Nope, the car has to be off for at least a couple of hours for it to kick back on. I'll try spinning the compressor pulley tonight (car's at home in the garage).
__________________
2002 BMW 330Ci, Benzless at the moment.

Past: 1994 E420, various W123 240D rustbuckets
Reply With Quote
  #12  
Old 07-07-2011, 08:38 PM
engatwork's Avatar
busy
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,643
I'm wondering if the clutch is dropping out after the compressor gets hot? I have seen this before. Are the components original? Feel the tension on the belt while you are under there to verify that it is pretty snug. What kinda shape is the tensioner in?
__________________
Jim
Reply With Quote
  #13  
Old 07-08-2011, 11:48 AM
pesuazo's Avatar
Registered User
 
Join Date: Oct 2002
Location: Near Raleigh, NC
Posts: 580
You are suffering the same symptoms I am.

I normally get 40F out the vents on a 95F degree day with 90% humidity (excellent) running on the highway. 50-55F at idle.

I am getting codes 5 and 6 in pin 8 of the diagnostic module.

You probably have the same.

In my troubleshooting, I changed the tensioner as well as the belt with no success.

I was observing the compressor cycle at idle, it was cycling fine. At about the tenth cycle, I noticed the clutch would start slipping and then stop (not engage, and A/C stops working) AHA !!

I think the clutch material is either wearing out, or the gap should be adjusted (in my case). I have not done it, but now I know why the A/C stops, sporadic clutch slippage.

You may want to check that.

Pedro
__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified
Reply With Quote
  #14  
Old 07-08-2011, 04:53 PM
Registered User
 
Join Date: May 2008
Location: Bellevue, WA
Posts: 36
Quote:
Originally Posted by pesuazo View Post
You are suffering the same symptoms I am.

I normally get 40F out the vents on a 95F degree day with 90% humidity (excellent) running on the highway. 50-55F at idle.

I am getting codes 5 and 6 in pin 8 of the diagnostic module.

You probably have the same.

In my troubleshooting, I changed the tensioner as well as the belt with no success.

I was observing the compressor cycle at idle, it was cycling fine. At about the tenth cycle, I noticed the clutch would start slipping and then stop (not engage, and A/C stops working) AHA !!

I think the clutch material is either wearing out, or the gap should be adjusted (in my case). I have not done it, but now I know why the A/C stops, sporadic clutch slippage.

You may want to check that.

Pedro
Hmm interesting.. the belt and tensioner are fine; I just checked. I'm planning on getting the system pressure tested Monday morning. Thanks for the tips!

__________________
2002 BMW 330Ci, Benzless at the moment.

Past: 1994 E420, various W123 240D rustbuckets
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 06:06 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