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 05-22-2010, 10:02 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
87 300D AC question

The AC compressor will not engage, everything was good and cold a week ago. The pressure switch is closed, the compressor turns easily by hand. However, the temperature switch appears to be open, if I am checking the right part. It's the second sensor to the left of the fuel filter. Here is a pic:



With the engine running (not hot at all) these two posts do not have continuity (open). Is this the temperature switch? And are these the switch terminals? It has another terminal on it with just one wire, just to the right of these two terminals.

If this is the temp switch, and it is open even with a cold engine, I should be able to short the two leads together and the compressor should start, no?

TIA for any help.

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #2  
Old 05-22-2010, 10:31 PM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,339
no idea on the particulars of this model yet, so I can't help you on the switch...
but, the likely cause of an 85+ model losing compressor function is the OVP relay, or the kilma... test them too!
Reply With Quote
  #3  
Old 05-22-2010, 10:32 PM
babymog's Avatar
Loose Cannon - No Balls
 
Join Date: Jan 2006
Location: Northeast Indiana
Posts: 10,767
That is a combination temperature-gauge sender and aux. fan switch. Should be open until the engine is hot enough for the aux fans to start.
__________________

Gone to the dark side

- Jeff
Reply With Quote
  #4  
Old 05-22-2010, 10:41 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
I have the FSM, it starts the troubleshooting procedure at the Klima socket, but it looks like I'll need to move the ECM out of the way to get to the terminals.
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #5  
Old 05-22-2010, 11:46 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
OK I pulled one of the PC's out of the way and proceeded with the dignostic testing of the Klima socket. First 3 tests all good, (12V power, pressure switch and electromagnetic clutch). Test #4 for the compressor speed sensor asks for a nominal voltage of at least 0.03 VAC between terminals 5&7, I got .24 VAC, a tad under. Going to the resistance test of the speed sensor, it asks for a nominal value of 530 to 650 ohms, I get 890 to 897 ohms. On test step 5 for the starter ring gear speed sensor, I it asks for at least 2.8VAC, I get almost 6 VAC at idle. Test step 6, the emergency cutout temp switch asks for a voltage of under 1 V, I was well under that, so no short there.

So the compressor speed sensor is a bit out of range, but I am wondering if it is really enough out of range to cause the Klima to cut the compressor, or if the Klima is actually bad.

Questions, should I just replace both, or start with the speed sensor? Does changing the speed sensor involve a system discharge?

Also, would it be OK to short the Klima terminals 5 & 7 temporarily until parts get here?

Finally, where is the best place to get my parts?

thanks for any and all help.

Brian, out here in the HOT desert.
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #6  
Old 05-22-2010, 11:58 PM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
Quote:
Originally Posted by dieselmania View Post
OK I pulled one of the PC's out of the way and proceeded with the dignostic testing of the Klima socket. First 3 tests all good, (12V power, pressure switch and electromagnetic clutch). Test #4 for the compressor speed sensor asks for a nominal voltage of at least 0.03 VAC between terminals 5&7, I got .24 VAC, a tad under. Going to the resistance test of the speed sensor, it asks for a nominal value of 530 to 650 ohms, I get 890 to 897 ohms. On test step 5 for the starter ring gear speed sensor, I it asks for at least 2.8VAC, I get almost 6 VAC at idle. Test step 6, the emergency cutout temp switch asks for a voltage of under 1 V, I was well under that, so no short there.

So the compressor speed sensor is a bit out of range, but I am wondering if it is really enough out of range to cause the Klima to cut the compressor, or if the Klima is actually bad.

Questions, should I just replace both, or start with the speed sensor? Does changing the speed sensor involve a system discharge?

Also, would it be OK to short the Klima terminals 5 & 7 temporarily until parts get here?

Finally, where is the best place to get my parts?

thanks for any and all help.

Brian, out here in the HOT desert.

My limited experiences in troubleshooting that system on the SDL generally leads me to conclude that the Klima doesn't act instantaneously. If it's dropping out due to a bad signal from one of it's input parameters, it generally will start the compressor for a short period of time (maybe 30 seconds) and then drop it out. It resets this behavior each time you shut the engine down and restart it.

So, you could observe the clutch and see if you get 30 seconds or so of engagement each time you select the middle button (compressor engaged).

If you get nothing, my bet is on a bad Klima itself. They are known to fail.

Yes, you can jump sockets 5 and 7 and the compressor will run all the time (and potentially freeze the evaporator in the process). It's better to setup a small relay using socket 10 as the ground signal from the CCU. When socket 10 gets the ground, the relay closes and provides power to the clutch. Under this setup, the evap temp switch still has control of the compressor clutch and the evap will not freeze.
Reply With Quote
  #7  
Old 05-23-2010, 12:12 AM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
Quote:
Originally Posted by Brian Carlton View Post
My limited experiences in troubleshooting that system on the SDL generally leads me to conclude that the Klima doesn't act instantaneously. If it's dropping out due to a bad signal from one of it's input parameters, it generally will start the compressor for a short period of time (maybe 30 seconds) and then drop it out. It resets this behavior each time you shut the engine down and restart it.

So, you could observe the clutch and see if you get 30 seconds or so of engagement each time you select the middle button (compressor engaged).

If you get nothing, my bet is on a bad Klima itself. They are known to fail.

Yes, you can jump sockets 5 and 7 and the compressor will run all the time (and potentially freeze the evaporator in the process). It's better to setup a small relay using socket 10 as the ground signal from the CCU. When socket 10 gets the ground, the relay closes and provides power to the clutch. Under this setup, the evap temp switch still has control of the compressor clutch and the evap will not freeze.
I realized after I posted that jumping 5&7 would result in the compressor running all the time, I was going to ask about bypassing the speed sensor if possible to see if that is the problem. However in light of what you said about the Klima letting the compressor run for a short time, I am leaning toward a bad Klima. The compressor never starts, not even for one second.
Where can I get one for a good price?

Thanks for all your help, I remember you from way back when I first got this car and I was obsessed with it. I haven't done much to it lately (especially since I got my Powerstroke) but it has been a very dependable ride for many years.
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #8  
Old 05-23-2010, 02:27 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
Since the rebuilt Klimas are $70 and new are $125-$150 I am considering a rebuilt. Any thoughts or experiences?
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #9  
Old 05-23-2010, 03:05 PM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
Quote:
Originally Posted by dieselmania View Post
I realized after I posted that jumping 5&7 would result in the compressor running all the time, I was going to ask about bypassing the speed sensor if possible to see if that is the problem. However in light of what you said about the Klima letting the compressor run for a short time, I am leaning toward a bad Klima. The compressor never starts, not even for one second.
Where can I get one for a good price?
We don't discuss parts suppliers on the forum as a courtesy to the sponsor of the forum, who can maintain the forum without charge solely because of the ability to sell parts.

However, if you'd accept the risks of a used part, they do appear on e-bay and on the parts section of this forum on occasion. However, be careful of the part number. Very similar gasser Klimas will not work on the diesel.
Reply With Quote
  #10  
Old 05-23-2010, 03:26 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
Got it. Thx.
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #11  
Old 05-24-2010, 09:16 AM
LarryBible
Guest
 
Posts: n/a
You are skipping the fundamental steps in your troubleshooting procedure. Have you connected gauges and checked pressures? A leak could easily have caused this problem. Step number one in ANY a/c troubleshooting procedure is a visual inspection, step two is connecting manifold gauges and checking pressures. You need to go back to step two before you go any further. Don't get the cart in front of the horse.
Reply With Quote
  #12  
Old 05-24-2010, 10:33 AM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
If there was a leak causing no operation, wouldn't the pressure switch be open? The pressure switch is closed, and even bypassing it won't engage the compressor.
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #13  
Old 05-24-2010, 11:47 AM
LarryBible
Guest
 
Posts: n/a
Sorry! My bad habit of quickly perusing threads reared it's ugly head.
Reply With Quote
  #14  
Old 05-24-2010, 08:51 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
I hear ya, do the same myself. And I just hate to drag out the gauges. The compressor and reciever are 3 years young and it's pretty clean under the hood, no visible leaks. A low charge was the first thing I thought of, but ruled it out with the pressure switch. I was extremely relieved too as I still have the original evaporator.
__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
Reply With Quote
  #15  
Old 05-25-2010, 11:34 PM
dieselmania's Avatar
Registered User
 
Join Date: Jul 2003
Location: Tucson, Arizona, USA
Posts: 566
Got the new Klima today and all is well. Thanks to all who helped.

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 110K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
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 07:20 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, 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