Hi All,

The a/c of my 2001 C200 CDI W203 has been giving me a lot of problems lately. Following is a short description of the issue and symptoms:
(1) The a/c wont start blowing any cool air till the coolant temp reaches 70-80 degrees celsius and thats about when the fan and compressor kicks in.

(2) After 4-5 mins of blowing moderately cool air(not chilling), it will suddenly start blowing normal air. At times, it blows hot air. This happens almost as soon as I start driving.

(3) If I drive around at a high speed with high RPM, the a/c sometimes kicks in again.. Only to give up again after 4-5 mins and then the cycle of normal or hot air is repeated again.

(4) This also coincides with the radiator fan running at slow/moderate speed and coolant temperature rising to around 90 degrees celsius. Its almost as if the variable speed function isn't working.

(5) I have had the system recently re-gassed and all leaks fixed. The low side pressure is at about 90-100 psi and goes upto 50 psi when the compressor kicks in... only to return back to 100 psi in a few minutes.

(6) One a/c mechanic suspects its a compressor issue and suggested to change it completely and the other one says its a control valve issue and is suggesting to change only the control valve. Tool Diagnosis(x431) done by both threw up almost nothing.

First Diagnosis: B1205 - Refrigerant stored pressure is too low(There was no gas in the system due to a leak, which was rectified before the 2nd diagnosis)
Second Diagnosis: No faults
Realtime Diagnosis:
381 Refrigerant Pressure and Temperature sensor B12/2 = 38 bar(This kept fluctuating between 30-40 bar in realtime readings)
382 Refrigerant Pressure and Temperature sensor B12/2 = 215 Celsius(This seemed way too high but the mechanic quickly disowned this reading blaming it on a fault with the diagnostic tool)
384 Refrigerant Compressor = 70%(This was almost stagnant till a/c was switched off)

(7) I suspect the pressure switch may be one of the culprits here, if not the only one, resulting in the radiator fan running slow and the rising coolant temperature. But the coolant temperature never goes beyond 90-95 degrees celsius(with outside ambient temp being 30-35 degrees celsius).

Before jumping in and ordering random parts, I need your valuable opinion on the following:
(A) Will a bad pressure switch/sensor throw up an error code? If yes, will it do so at all times and as soon as a plug in a diagnostic tool or do I need to start the a/c and let it run for some time, etc.

(B) If no error code has been detected, can I safely assume the pressure switch/sensor is working fine?

(C) Similarly, will a bad compressor control valve throw up an error code and is it a good idea and a relatively easy task to replace the control valve or shall I replace the whole compressor?

I have narrowed down on the following valve for the denso 7SEU16C compressor but the 90 degrees angle at the top worries me. Will it fit or cause an obstruction?
http://www.ebay.com/itm/New-Compressor-Control-Valve-90-For-DENSO-7SEU16C-7SEU17-AUDI-A3-VW-/261261180979?pt=Motors_Car_Truck_Parts_Accessories&hash=item3cd4614033&vxp=mtr
Or shall I go for this one, which seems to be straight at the top:
http://www.ebay.com/itm/SANTECH-IND-MT2258-A-C-Compressor-Control-Valve-/130856143862?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e77a24bf6&vxp=mtr
(D) Anything else I'm missing or any observations or suggestions on the proposed line of action are most welcome. Thanks a lot in advance and sorry for the long post.

 

Hi All,

Today I tested the A/C high and low side pressure and following are the results(in psi):

Engine Off/AC Off - Low Pressure=100, High Pressure=120
Engine On/AC On - Low Pressure=60, High Pressure=225

As you can see, the low pressure hardly moved even though the high pressure went all the way to 225 psi and even though the pressure was 225 psi, the radiator fan was moving at a very slow speed.

I disconnected the coolant temp sensor wire momentarily to force the fan to kick in at full speed and it sure did resulting in cool air finally blowing inside the cabin. It wasn't as chilled as expected though(this maybe due to under or over charging of gas or many other reasons but I chose to ignore it as getting the a/c to start functioning normally is the primary objective as of now, amount of cooling can be addressed later).

Following are the pressure readings with the radiator fan on FULL(100%):
Engine Off/AC Off - Low Pressure=110, High Pressure=180
Engine On/AC On - Low Pressure=40, High Pressure=150
Engine On/AC On/Coolant sensor re-connected) - Low Pressure=60, High Pressure=205

As expected, the low pressure increased and the cooling almost stopped as soon as I plugged the coolant temp sensor wire back.

Can we rule out the a/c compressor and/or control valve based on the above results?
What else can be ascertained from these results, Thanks

 

Can I use a 7SEU17C compressor instead of a 7SEU16C compressor on my C180. I can't find a 7SEU16C denso compressor and my mechanic says the 7SEU17C will fit?