anikon

Hi,

Couple of days ago I noticed that the temperature is going high. After couple of tests I realized that this is because the AC is on.
The problem is: if the AC is on, the 2 front fans doesn't start and the temperature is going high 110-115F (maybe more if i leave AC on more time).
I checked it with a mechanic and we couldn't fix it. The following were checked:

• 1. Replaced with a new temperature switch (4 pins) located in the thermostat case near the temperature sensor
• 2. The fans works fine if connected at 12V
• 3. The green relay (from relay box) works fine (we replaced with a new one)
• 4. Filled with refrigerant. The AC is working fine (ice cold)
• 5. All fuses are OK

Do you have any idea what else should be checked/replaced? I read on the forums that there is also a "dropping resistor". Can you tell me where is located? (Some pictures are more than welcome).

So, if i drive with AC off, the temperature is normal (around 90F). These days i drive without AC but here in Florida it's very hard without AC. I just want to be able to drive with AC.



Thanks.

vinceC

Info in addition to my response to your PM. Some things to check:

1) 12V at connector X12/3. It is under a plastic cover right in front of the main fuse box F1. It is an unfused 12V supply. This is unlikey a problem, but check anyway.
2) There should be a 10A fuse in the main fuse box F1 that is for the activation circuit for the relays. Not sure which one at this point - there should be a card under the fuse box cover. This can affect both fans.
3) There is a connector for the fans at the upper left hand corner of the plastic grille in front of the fans. Check for power.
4) The command to the relays comes from N22 - the ACC Control Panel on the center stack. Connector 2, Pin 7 is supposed to be the activation command circuit to the low speed relay (Relay Pin 5). Connector 2, Pin 16 is supposed to be the activation command circuit for the high speed (Relay Pin 5). I say "supposed to be" because I think the functions may be reversed - there is some conflict in the literature I have.

anikon

Thanks a lot Vince for the reply and email. Saturday I'll check everything you have suggested (I bought some tools these days).

In addition I uploaded some pictures of all parts which may be the cause of the problem (just to be here for future )

I'll let you know after i check everything.

PS: Vince, can you put some pictures or a schema (if possible) with connector X12/3 and N22?

vinceC

The attached phots are of X12/3. You really can't miss it - it is directly in front of the fuse box.

N22 is the pushbutton panel in the center console. There are two small screws under the bottom edge of the wood and two above the radio, inside the opening. You have to pull the radio (using the radio removal keys). Four screws hold the whole panel to the plastic frame behind the wood. The connectors are on the back. I don't know which one is Connector 2. Look carefully - it should be marked.

I don't have the means to scan documents. I work from the M-B W202 CD (P/N P-2700-202-03). Security on the CD prevents me from printing PDFs and as I stated I don't have the means to scan hard copies.

vinceC

I've been poking around on my CD a bit. My car doesn't agree with either date group, so yours may not either, but the 10 amp fuse (shown as position 31 on the CD) may be a 7.5 amp in position 11. Instead of 12V from X12/3, there may be a 30 amp fuse in position 13 of F1 (that is a row of fuses down the center of the fusebox that is technically F2).

Good luck.

anikon

Hi,

I checked the car at MB service in Fort Lauderdale and the problem is the A/C Central Unit (push buttons). They said that it's something wrong with the unit.

Total cost to replace it: $1000. I'll make some research to see if I can change it cheaper.

I'll let you know what I did.

vinceC

Check Potomac German Auto (a recycler). This week I can check a body shop nearby that has a few W202 C-Class in the yard.

vinceC

Another suggestion: http://www.beckmanntechnologies.com/products.html

anikon

Hi,

After I read couple of threads about Climate Control Unit / How to diagnose AC system (http://www.mercedesshop.com/shopforu...t=40964&page=2), I tried the self diagnose tool of the climate control (Press REST for couple of seconds until some codes and values appear on the screen).

Now it's too late to do much (it's 23:00 hour), but tomorrow I'll check again all codes and values to see which is the problem. Maybe I'll delete the codes after that.

I'll let you know how's going.

anikon

Hi,

I read the CCU codes/values for my January 1995 C280. Here they are:

Code 1st Reading 2nd Reading
01...........102F...........97F
02...........93F...........93F
03...........91F...........77F
05...........71F...........66F
06...........20 0...........21 3
07...........17 1...........22 8 ... max was 27 8
08...........45 0...........45 0
09...........03...........03
15...........LO...........66F (i changed the INSIDE temp from low to 66 between readings)
20...........02...........02
21...........06 9...........07 0
22...........08 4...........08 4
23...........00 0...........00 0
50...........10 C
51...........00...........00
52...........00...........00

Here is the Code meaning: http://www.mercedesshop.com/shopforu...d.php?p=234367

From what I read on these forums number 7 and 50 seems wrong.

What do you think?

PS: I couldn't clear the codes by pressing '^' and 'v' the same time.

Do you think I should replace the Climate Control Unit?

Another issue is how can I remove the CCU (I search other threads by i couldn't find something suitable for 1995 C280). The hard part is removing the wood trim around CCU.

Thanks.

vinceC

I don't think the data tell you much about the command to start the fans, except that 07 - Refrigerant Pressure is high and that should cause N22 to send a command to start the fans. Also, if I am not mistaken, you have not read the fault codes - you have read live data. There is a difference. I extracted fault codes on my '95 once, but can't remember the procedure. Try a search on posts by David C Klasse over on mercedesshop. He had a '95 and did some fauly code reading if I remember correctly.

I mentioned how to get the wood off earlier:

"N22 is the pushbutton panel in the center console. There are two small screws under the bottom edge of the wood and two above the radio, inside the opening. You have to pull the radio (using the radio removal keys). Four screws hold the whole panel to the plastic frame behind the wood."

anikon

The radio can be removed only using the "radio removal keys"?

Do you have any idea where can I find these keys?

anikon

Hi,

I want to connect the 2 fans directly to the battery and put a on/off switch on the wire. I'll use some high temperature wires.

I want to do this as a temporary solution until I replace the CCU. I just can't drive without AC these days in South Florida

Where can I connect the wires inside the engine compartment (I don't want to connect directly with the battery because it's in the trunk)? X12/3 connector is OK?

I'll put also a fuse on the wire.

What do you think?

Thanks a lot.

vinceC

This is a link to a supplier for the radio tools. There are all sorts of suppliers, maybe even your local auot parts store.

http://www.zdmak.com/wbstore/main.as...ST9000A&CTMP=1

As for the "hot wire" idea, I don't know if it will work or not. It depends on whether N22 is sending a command to the compressor clutch to engage. The fan problem may or may not be combined with otehr problems. Try a fused lead from X12/3 a see if it works.