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2002 Mercedes slk 320 AC not blowing cold, compressor clutch…

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2002 Mercedes slk 320...

2002 Mercedes slk 320 AC not blowing cold, compressor clutch not engaging, r134 level good, if i unplug the pressure switch on the dryer and plug it back in, the compressor will engage for about 20 seconds then disengages again.

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Submitted: 2 months ago.Category: Mercedes
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Answered in 1 hour by:
5/2/2018
Mercedes Mechanic: Matt, Engineer replied 2 months ago
Matt
Matt, Engineer
Category: Mercedes
Satisfied Customers: 23,305
Experience: Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Hello and welcome to Just Answer

1st thing to check is that the AC rad / condenser is clear of any debris and there's nothing in front of the air flow to it, next ensure that the AC pump drive belt isn't slipping and if any doubt replace it.
Also check that if there's a pollen filter to the cabin air inlet that this is clean and free flowing
Next you can test components simply by checking the temperatures by touching them with the system running. with the engine at operating temperature and the AC turned on it should be as follows:
A hot compressor / pump
A hot high pressure refrigerant line from the compressor to the condenser
A hot condenser on the inlet
A warm condenser on the outlet
A warm liquid line from the condenser to the evaporator (before the expansion valve or orifice tube)
A cold evaporator outlet line
A cold low pressure refrigerant line to the compressor

If you get a different result from the above then suspect a blockage in the line or the component whose temperature is abnormal, this can be confirmed with a pressure test

Then if you're happy the temperature control is OK ( does it do hot as well as cold?) I'd take the car to an garage that can read the pressure levels of the system so the level of gas can be checked hopefully all it needs is a re-gas

from your description I'd say either there's a blockage in the system or the pressure switch is faulty

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Customer reply replied 2 months ago
Did you read the question?
The clutch is only engaging for 20 seconds if the pressure switch is disconnected and reconnected. I don't think debris in the condenser, pollen in the filter, or a slipping belt will cause the clutch not to engage, nor is there any point in checking any temperatures of the clutch is not engaging... Useless answer.
Mercedes Mechanic: Matt, Engineer replied 2 months ago

Ok if the pressure switch is faulty it will give this issue as the system takes a 'sample' measurement over several seconds so it won't just switch the clutch off straight away

so this is why I suggest to check for blockages in the system by feeling for hot cold lines etc

If you're confident this is all OK then I'd say to replace the pressure switch and then also check the wiring from the pressure switch for any damage

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Customer reply replied 2 months ago
What about the evaporator temperature sensor?
Mercedes Mechanic: Matt, Engineer replied 2 months ago

That shouldn't turn the compressor off however if its shorted out I suppose it could give a false reading and show the evap is down below the set point ? however when they fail its normally to go high so the fans and compressor are on all the time?

Try this method to pull off the AC diagnostic code:

Turn ignition on. Press down arrow push button until “LO” is shown in A/C-heater control panel temperature display window.
2) Within 20 seconds, simultaneously press REST and defrost push buttons for more than 2 seconds. The Light Emitting Diode (LED) in the recirculated air push button will blink and the display window will show “di R”.3) Press AUTO push button repeatedly, recording each DTC,until all DTCs are displayed. Permanent malfunctions are displayed first. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION tables.
4) If no permanent malfunctions are stored, the display window shows “En d”. Press AUTO push button again. Intermittent DTCs will be displayed. Intermittent malfunctions are recognizable by the degree (°) symbol displayed along with the DTC (example: “04 °”).
5) If no intermittent malfunctions are stored, the display window shows “En° d”. Proceed to ERASING DIAGNOSTIC TROUBLE CODES.

Erasing Diagnostic Trouble Codes
1) After display window shows “En° d”, press AUTO push button once again. Display window should show “dE L” (delete).
2) To erase DTCs, simultaneously press down and up arrow push buttons for more than 5 seconds. The display window should show “- –“. If not erasing DTCs, press the AUTO push button. The permanent DTCs will again be displayed. Proceed to EXITING DTC DISPLAY MODE.
Exiting DTC Display Mode

Simultaneously press down and up arrow push buttons until the pre-selected temperature setting of “72 °F” is displayed. Turn ignition off.

DCT error codes list:

B1226 – In-car temperature sensor (B10/4)
B1227 – Outside temperature indicator temperature sensor (B14)
B1228 – Heater core temperature (B10/1)
B1229 – Heater core temperature (B10/1)
B1230 – Evaporator temperature sensor (B10/6)
B1231 – ECT sensor (B11/4)
B1232 – Refrigerant pressure sensor (B12)
B1233 – Refrigerant temperature sensor (B12/1)
B1234 – Sun sensor (B32)
B1235 – Emissions sensor (B31)
B1241 – Refrigerant fill
B1416 – Coolant circulation pump (M13)
B1417 – Duovalve (Y21y1), left
B1418 – Duovalve (Y21y2), right
B1419 – Electromagnetic clutch (A9k1)
B1420 – Idle speed increase
B1421 – Pulse module (N65)
B1422 – Series interface (K1) connection to instrument cluster (A1)
B1423 – Switchover valve block (Y11)
B1424 – Activated charcoal filter actuator (A32m2) open
B1425 – Activated charcoal filter actuator (A32m2) closed
B1432 – Non-USA DTC
B1459 – Series interface (K2) connection to instrument cluster (A1)
B1462 – Wide open throttle (WOT) position signal: diesel engines

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Mercedes Mechanic: Matt, Engineer replied 2 months ago

Hi
do you still need help?
Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! If you're not pleased, also let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent further replies
Thanks Matt

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