[NightBlue]

Gents,

I've been doing a whole bunch of reading trying to figure out an AC problem I have on a 1998 S320. Car has 150K miles on it. The system had been trouble free up until this summer.
The climate control unit powers up intermittently (fan blows when it powers on, when its off...no fan)The fuses: 17, 18 and 20 are all good and they all maintain voltage when the module powers on or off. Left and right module plugs seem fine. I have tried other climate control units from parts cars. The AC clutch is not coming on. (I have 9v on the wire coming to the clutch, no change when module is on or off) I put the AC gauges on the system.....I have proper pressure.

I have not ohm'd out the clutch. I have not verified ground, on the compressor. I have not verified the clutch wiring (very dirty and greasy down there) I will be doing this tomorrow.

Questions:

I have reviewed K6JRF's site and I understand that the procedure for finding stored codes, from the climate unit, is the same for the early version and for the late version. I haven't figured this out yet. Can anyone give some more info on this, (I have also read many links)?


NightB
1997 S420
1999 ML430
1984 300CD
1984 450SL
1995 S420
1994 S350 (with a 606 engine)

 

[Hussain995]

The procedure is as follows:
Set the left temprature to hi and the right to lo then switch the ignition off/on, press and hold the rest and EC buttons until the recirc/fresh air button starts flashing. Then you cycle through with the auto buttons. Delete the faults by pressing both Auto buttons at the same time.
I know this to work on my 98 model.

I had this problem before and it was intermittent. Replacing the pushbutton control module fixed it for me. But you say that didn't work for you.

Ps: I used to get a fault code for th compressor clutch..even though there was nothing wrong with it.

Good luck.

 

[NightBlue]

Thanks for the reply! I understand the procedure now.

Will get on it tomorrow.

Thanks again. Will report my findings.

NightB

 

[NightBlue]

My Findings............

I have a good ground to chassis for the AC compressor.
I ohm'd the AC clutch-------4.1 ohms.
I only get 5 volts from the wire going to the compressor, once the car is started I'm getting 5 volts. No change in voltage.
If I hotwire the compressor with battery voltage, the compressor starts and runs properly. I believe I had a reading of 7 bar from the control module readout for the freon pressure.

I pulled another climate control module from a 1997 S420 parts car that I have. I installed it, no change, the blower would not start.

I pulled the DTCs for the climate module:
1227-outside temp sensor
1231-ECT sensor- coolant temp sensor B11/4

I have ordered an ECT sensor, will arrive tomorrow.



Thanks

Night B

 

[MAVA]

Have you tried to drive the clutch directly?

From the diagnostic data it appears the climate control drives the clutch directly, but I thought the module(N65/1) on inside drivers bumper did the driving of the clutch, and I could be dead-wrong on that. Somewhere I saw that is what recollect somewhere...

The compressor is A9-K1, and the signal should be coming from pin 25 on connector 2 from the climate control unit.

The diagrams and procedure are for all +96 cars

Let us know what happens..

Martin

 

[NightBlue]

Additional info:

My sensor values are as follows:
1--94 degrees, in car
2--40 degrees, outside temp sensor.....(probably broken) need to repair !
3--114 degrees, left heater core
4--104 degrees, right heater core
5--94 degrees, evap temp sensor
6--40 degrees, coolant temp sensor, (new one is ordered)
7-- 8 bar, refrigerant pressure
8--93 or 9.3, blower control voltage
9--0, software status


NightB

 

[NightBlue]

MAVA, Glad to see you chimed in.......... Like I said, I've done a bunch of reading so far.

YES.......I did hot wire the compressor.........she runs fine when hot wired. !!

Thanks a bunch for the last three attachments, I can now start to really trouble shoot what is going on. I've already printed the legend and the diagnostics and sent the wiring diagram to my iPad. I have an alldatadiy subscription for this car.........there is a lot of info to comb through on those pages.


Thanks,

NightB

 

[NightBlue]

MAVA,

One more thing........I thought that the base module gets a signal from the ACC module and subsequently sends voltage to the clutch.......??

NightB

 

[NightBlue]

N65/1 AIR Control Module

MAVA, I did some more research on the AIR Control Module:

The auxiliary fan control module switches on the auxiliary fan.

The pushbutton control module controls the AIR control module (N65/1) with a minimum of 3 mA and max. 10 mA .

The AIR control module (N65/1) compares these values with stored values and switches on the auxiliary fan (M4) under the following conditions:

Outdoor temperature >5 °C
Refrigerant pressure = 13 bar
Coolant temperature = 103 °C
Limp-home mode (e.g. refrigerant pressure > 20 bar )

The auxiliary fan (M4) is switched off under the following conditions:

Refrigerant pressure = 12 bar
Coolant temperature = 100 °C

 

[MAVA]

Thank you for your comments, but MAVA is no genius at AC. I'm dangerous...

If you get 5v, is that level under load? or open circuit? A friend of mine whose AC works fine on his 93 had some chaffed wires rubbing on the sub frame next to the compressor, and that may be your problem too. If you check the loaded output at pin 25 connector 2 with 4ohm or so resistor(30 to 50watt)the line to the AC disconnected. if you are feeling cheap, use a small extension cord to the compressor to the climate control to by-pass the cars wiring..

Martin

 

[NightBlue]

I got the 5 volt reading from the wire that goes to the compressor. I unplugged the compressor and measured the voltage at the plug. I will ohm out this wire. I will remove the no. 2 connector at the N22 module and measure it against the chassis. I will then measure the voltage coming off of the pin u mentioned.

I will also start the trouble shooting procedures that you sent.

I accessed the P1 and P2 coding on the climate control module today. I know that the module in the car is not the original to the car. I don't know where it came from. I don't remember what P1 was set to, but I set it at: 01. I then moved on to P2, it was originally set at 128. I set it to 137. (if I am wrong with my numbers....someone please, let me know). I then turned the ignition off and tried to get the blower to work. I still have no air movement in the cabin.

I used the information that syljua provided, for coding, from a January 2014 thread (Post number 7): http://www.benzworld.org/forums/w140-s-class/1442153-w140-plug-n-play-i-think.html#post3462815

I need to figure out why this module is not powering up !

Thanks again for the help.

NightB

 

[Drbobme1]

Per post #4 and #6 the outside temp and ECT are bad. Reading 40.With the controller seeing those low reading 40 degrees it will not turn on the blower or operate the compressor. Repair/Replace them. Check sensor plugs and wiring.

 

[NightBlue]

ECT Sensor and outside temp sensor

Drbobme1,

I changed the ECT sensor.

I checked the values of all the sensors in the climate module (N22), they are now as follow:

1---91
2---84 (outside temp sensor)
3---92
4---97
5---88
6---111 (ECT sensor)
7---8
8---87
9---0
10--2.7
11--.5
There are the remaining numbers to report, I will not report them now.

As we can see the ECT and the outside temp sensors are working.

When I started the car and turned on the Climate Control to Auto---I started to get blower activation, full speed, I then checked the AC compressor clutch. IT IS RUNNING. (I checked voltage.......I have nine volts) After about 10 seconds the blower stopped blowing, but the compressor clutch stayed engaged. ???????

I then thought about checking and setting the codes, P1 and P2 settings.

I am a little unclear about where the numbers should be. I set P1 at "01" and P2 at "137". I tried the system again. NO BLOWER and clutch engaged.

I then set P1 at "73" and P2 at "09"...........NO BLOWER and clutch engaged.


Thoughts ??

Thanks to all

NightB

 

[Drbobme1]

I have a 99 S500 so the coding is different.

Coding up to 1997

P1: 01 Fahrenheit
03 Celsius
72 Serial interface K1 and K2

P2: 02 M119 (up to 1997)
+8 to engine version (Blower motor bar graph switched to auto mode)
+128 to engine version SMOG (display readout switched off)

Suggest you change your P2 to 02 or 10



Hope this helps

 

[mrboca]

Check the blower regulator.

 

[NightBlue]

Wrap up

Gents,

I have four climate control modules. I narrowed the field down to two which had good buttons for all functions. Of these two there was only one that would activate the AC clutch. I tried different coding sequences. I think I settled on 01 for P1 and 09 for P2.

I'm sitting in the hot car scratching my sweaty head.......trying to think of what I'm missing. So, I start thinking about the blower itself. (I wasn't logged on to the computer and didn't know the latest suggestions that were being posted) So, I had a spare blower.......I installed it.......started the system. I now had a constant fan.......low speed only. Now I'm thinking blower regulator.

I took a 30 min drive to my 97 S420 parts car and grabbed the blower motor and regulator. I installed it and........VOILA !!! Full fan, all the speeds, clutch still engaged and cooling like a champ!

Recap: The ECT sensor was shown to be bad during the climate control diagnosis, along with the outside temp sender. When you look at the wiring diagram that MAVA supplied you can see that the ECT and outside temp sender kind of work hand in hand with each other. Once I changed the ECT (coolant temp sender)........both of these values came into proper range, for the N22 module to use. The blower regulator was the last piece of the puzzle that needed to be put into place.



Thanks for all the valuable and timely information.


NightB