Total Failure of Climate Control Air Distribution in 95 C280
 

Well... I have been "touching the surface" on this matter for some time, as I've had a leak in the system.

Recently however, I realized that I have no control over the air flow. All airflow is directed to default (defrost & outboard dash vents) at all times, regardless of manual air flow selection or AUTO, or selected in cabin temperature. I am able to hear a faint clicking from the dash when I attempt to divert the air to the dash vents or the floor, but no action... same with RECIRC. The "default" air passage (defrost & side vents) blows outside air... and the faster I'm driving (IE: fwy), the faster the air blows.
Also prior to the complete failure, if I had the A/C on, air would stop blowing through the dash vents when I accelerated, and then would properly start flowing back through the dash vents upon deceleration or coasting.

I have retrieved the climate control fault codes, and am consistently coming up with 28 and 60 only. I delete them every few days, and those are the only 2 that recur (intermittent, fortunately).


The 2 recurring codes are:

28: Well I can't find the meaning of 28. I have been searching the archives with no luck; I don't understand? I just finished sifting through some 2500 posts of mine! I know the info is in the archives. Argh, oh well.

60: A/C Compressor Electromagnetic Clutch (A9k1).
Cause: Short or Open Circuit. Intermittent (not continuous).
This doesn't seem to be vacuum related though...(see following link for more depth on this)

http://www.peachparts.com/shopforum/tech-help/21711-c-diagnostics-codes.html?highlight=clutch+continuous


Just for fun:
http://www.a-p-group.com/cklasse/Con....DrawingCC.jpg

Climate control difficulties
 

David
We've talked before on other problems. Now I seem to be having the same problem with my '95 C280 as you describe in yours. I have the additional symptom having a variety of air temperature flow from different vents. Have you had any suggestions or ideas on a resolution?
Incidently, some time back there was a high pitch wheezing sound coming from under the glove box. I wiggled some apparent vacuum gadgets back there and the noise went away. I wonder if my current difficulties are related to that.
As usual, any help will be apprciated. Bob H

David:

I realize my situation may differ from yours in that my vehicle is a different yr/model, but..............

Not long ago I too had a default air flow situation similar to yours. I traced it to a fuse that wasn't blown, but had somehow become unseated.

Worth a shot I suppose.

The air distribution system is vacuum operated. The source is the engine. Check to see if the switchover block is operating. If it is, then there is probably a vacuum line loose. I had the same problem with the air distribution system before, the vacuum line that connects to the intake manifold had disconnected. Check to make sure that there is a vacuum source for the system first.

Ali, thanks for the lead.....

but I don't know where these vacuum lines are!? Could someone please give me some more specific info on what to do? and how?!

Thanks again.

On my 97, there is a grey line near the fire wall that runs along the wiring harness from the passenger to the driver side. It then branches off and connects to the intake manifold. This is where is came loose on my car. Trace the lines around to make sure everything is connected.

Thanks Ali, I will check it out. I am assuming this is in the engine bay.
I'll keep you posted.

hey guys, I just fixed a 95 c 280 with the same symptoms. is the vacuum pump in the trunk cycling? there is a vacuum block in the right rear side of the engine compartment under the black cover that covers up the hand held computer hook up. 1st check to see if it cracked. 2nd if you have a vacuum tester, remove the glove box & the lower panel under it. behind the crossbar reinforcement is the vacuum switch over valve. remove the lines & test which one leaks vacuum. mine was the center vacuum element located under the left loer panel under the steering wheel against the heater box.

These are hard on defroster elements, recirc elements and floor elements. Odds are if the manifold assist pump functions, vacum block is solid and you have good engine vacum to the switchover block, you'll find a dead element that finally went completly feetup.


Joe

W202 chassis DTC 28
 

up to 8/95 is stated as: Refrigerent Pressure Sensor (B12); short circuit intermittantly

60 is: A/C compressor Electomagnetic clutch (A9k1); s/c intermittant

Thanks Jim!

Well none of the stored codes are vacuum related.

Wouldn't you THINK that if I have serious problem with the vacuum that it would store a code, or FIVE!!?

??? THx :)

no a vacum leak probaly would not trip too many computer codes....the cause of the stored codes could indeed be caused by a vacum leak(I think)......have the same problem with a 95 S320,throttle the car hard and the climate doors close due to the lack of vacum,during cruise it is fine

Well I have searched all over under the hood for any sort of loose or disconnected vacuum lines, and I can't seem to find any.
I'm just going to take it in to the dealership for the repair.
Thanks for the help everyone... and I will keep you all posted on the results.

Thank you! :D

Every c class I check AAC codes in has that pesky "electromagnetic clutch" code. I've gotten to ignoring that one. Vacum leaks will cause the following syptoms....

1 loss of airflow from desired vents

2 higher than normal output temps and loss of center vents on medium throttle.

3 the first time this one happened, transmission shifting harder with a/c on....... 5 hg loss to the modulator.

4 continous cycling of the manifold assist pump and eventual burnup of the pump which leads to loss of central locking.

Testing is pretty simple, remove the glovebox liner and the lower dash on the r/h side, get out your handy roadmap, remove the line block and start leak testing the elements. Also put a guage on the inlet side and watch the guage while operating throttle, it should stay pretty steady if the supply side of the system is solid.


Joe