Quick question... An easy one, I promise! :) - PeachParts Mercedes-Benz Forum

Christine in FL · #1 07-31-2010, 12:42 PM

1996 E320. There are three wires coming from the a/c low pressure switch:

1. Brown/White
2. Blue/Red
3. Red/White

Which two of the three do I jumper out to engage the compressor clutch?

Thank you!

Christine

duxthe1 · #2 07-31-2010, 01:09 PM

If I'm remembering correctly on that model it's not a pressure switch, it's a pressure sensor. As such you won't be able to jumper it. The ACC is going to need to see a value that it interprets as sufficient pressure to engage the compressor. Do you have a gauge set to see what your pressure is in the system?

david s poole · #3 07-31-2010, 01:22 PM

you can't jump them to bring on compressor.duxthe1 is correct.

Christine in FL · #4 07-31-2010, 01:33 PM

Quote:

Originally Posted by duxthe1

If I'm remembering correctly on that model it's not a pressure switch, it's a pressure sensor. As such you won't be able to jumper it. The ACC is going to need to see a value that it interprets as sufficient pressure to engage the compressor. Do you have a gauge set to see what your pressure is in the system?

Yes, I have a gauge set attached to the low pressure side. Pressure on the low (suction) side is 80psi. I haven't been able to locate a high side port to connect to though, so I was going to rely on the a/c diagnostic display.

Christine

Christine in FL · #5 07-31-2010, 03:10 PM

Here are the codes that I'm receiving from the display:

Key on engine off:

Eb1 233
Eb1 419
Eb1 232
Eb1 233
Eb1 419
Eb1 FF

Key on engine on:

Eb1 233
Eb1 419
Eb1 233
Eb1 FF

Here are the codes I received from the display with the engine on after holding the REST button down for 5 seconds:

43- 112
42 08
41 19
40 60
24 13.3
23 00
22 00
21 07
20 0.0
12 4.1
11 3.5
10 4.5
9 22
8 E
7 05
6 85
5 44
4 44
3 44
2 35
1 45

Can anyone explain what these codes are for me?

Christine

deanyel · #6 07-31-2010, 03:21 PM

Code list on page 110 here - http://www.motodok.com/Documentation/Files/MB/cs1000-mb.pdf

Christine in FL · #7 07-31-2010, 06:12 PM

Quote:

Originally Posted by deanyel

Code list on page 110 here - http://www.motodok.com/Documentation/Files/MB/cs1000-mb.pdf

Thanks! That will help quite a bit. Here's another link that might help anyone else that finds themselves in this situation:
http://www.continentalimports.com/ser_ic40142.html

After chasing down all sorts of information regarding the a/c control system this afternoon, I've narrowed my problem down to the clutch. I've confirmed 14VDC all the way down to within 12" of the compressor, yet the clutch isn't engaging. I suspect that there is a fusible link located either on or closer to the compressor. Hopefully it's just a bad fusible link and not a toasted compressor or clutch. I have a bad feeling that "Black Death" might have finally paid my car a visit though.

Christine

macdrone · #8 07-31-2010, 06:14 PM

put 12 volts right to the compressor, if it engages its a relay of pressure sensor issue.

Christine in FL · #9 07-31-2010, 06:58 PM

Quote:

Originally Posted by macdrone

put 12 volts right to the compressor, if it engages its a relay of pressure sensor issue.

I stuck a needle through the lead immediately before it enters the clutch and read 14.1VDC with the engine running and a/c on, yet the clutch isn't engaging. The ground is good also.

duxthe1 · #10 07-31-2010, 07:00 PM

Sometimes the wire breaks off right at the pin socket for the compressor's connector. Pry open the connector and make sure the wires are solidly connected to the pin sockets.

Christine in FL · #11 07-31-2010, 07:30 PM

I'm already downstream of the connector. I'm taking readings right at the point where the lead enters the clutch itself.

Just as a note, I measured 15.4 ohms of resistance from the clutch's hot lead to common with the key off.

Is there a possibility that the clutch may be corroded or stuck open? This car did sit in the garage for several months without being operated.

duxthe1 · #12 07-31-2010, 11:57 PM

15 ohms seems a little low but the clutch coil doesn't have a lot of resistance. I was thinking around twice that but I'm not sure of the spec at the moment and 15 ohms may be just fine. If you put power directly to the coil lead you should be able to hear an audible snap as it engages (engine off). If not you can safely assume the clutch coil is shot. Usually they fail in operation and not from sitting but in such a salty environment as the Keys I'd think it would become more likely. FYI, if the clutch coil is bad, you can do the job without opening the system. With the mounting bolts out the compressor will tilt down enough to get the clutch snap rings on and off. Make sure to not lose the shims that set the clutch air gap, they are small, thin, and easily misplaced. If yours is anything like the last one I did, you'll curse the cap screw phillips that hold the bracket to the top of the compressor. If you opt for a new clutch it will come with hex head phillips screws that should have been there in the first place.

Christine in FL · #13 08-01-2010, 12:13 AM

Thanks for your help. Before I completely give up on it, I'm thinking that I'll try tapping on the clutch lightly while momentarily applying power to it. If it is stuck or slightly jammed for some reason, that may free it up. I suspect that using any type of spray lubricants would probably be a bad idea due to the nature of the clutch's function.

duxthe1 · #14 08-01-2010, 12:50 AM

Not to be a downer but under almost all circumstances (barring physical damage that would be visable) the clutch is an all or none kind of deal, assuming no one has messed with the air gap. The part that moves, moves by flexing. There is no friction involved in its engagement motion. If the coil generates a sufficient magnetic field then the clutch head will flex and bring the friction materials in contact.

There's nothing to lose at this point by giving it what for with a hammer. If nothing else it may make you feel better given all of the greif this car has given you recently

Christine in FL · #15 08-01-2010, 01:14 AM

I wasn't aware of exactly how the clutch worked internally, I just knew that there was a coil involved. If it's shot, it's shot. It certainly can't be as tough to repair as the transmission was!

That was a real bear of a job, especially since I don't have the use of a vehicle lift. If you don't mind me asking, approximately how long did it take you to replace your clutch and do you know of any links to articles that might help me?