2017 Mercedes Benz C 43 AMG Diagnostic and Repair# S-83_55-118 Date: 090310

A/C - No Or Low A/C Cooling Performance
Date: March 10, 2009
Order No.: S-B-83.55/118
Supersedes:
Group: 83.55
SUBJECT:
All Passenger and Light Truck Models
Defective Refrigeration Circuit / Refrigerant Compressor
If you receive customer reports in the above model vehicles related to "no or low AC cooling performance", it may be due to a locked refrigerant
compressor, a broken torque limiter on the refrigerant compressor, the refrigeration circuit blocked or an electrical defect in the refrigerant
compressor. To remedy any of these issues please proceed with the following.
Note:
This document is intended as a supplement to the SDS function test "Refrigerant circuit test". Only perform repair and replacement work on the
refrigerant circuit if the SDS refrigerant circuit test was unsuccessful and you have received appropriate instructions in the SDS function test.
Prerequisites:
1. Before parts can be replaced, the exact quantity of the refrigerant in the refrigeration circuit must be determined by evacuating the system. When
returning parts be sure to indicate the exact amount of refrigerant in the circuit and any other findings by the technician. If the filling capacity is not
indicated, warranty claims may be rejected.

1. If the fill level of the refrigerant circuit is too low, parts should only be replaced if the torque limiter is broken.


2. If the fill level of the refrigerant circuit is too low and the torque limiter is damaged, the leak test (Test 6 "Leak in refrigeration circuit") must be

performed using the "Technology Guide Vehicle Climate Control" located in SDS SDMedia first and then the system must be refilled and checked.
If the amount of refrigerant in the circuit is less than 80% of the normal level, it is too low. Inadequate fill levels may be the cause of the air
conditioning shutting down or malfunctioning.
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Remedy A - Broken Torque Limiter:

1. Ensure the alternator freewheel (when applicable) is not damaged and that the belt pulley of the refrigerant compressor rotates in the belt drive.


2. If the alternator freewheel is blocked, replace the alternator freewheel. For refrigerant compressors with a replaceable belt pulley, replace the belt

pulley only, otherwise replace the refrigerant compressor. Refer to EPCNet for applicable part number.
3. If the alternator freewheel is not blocked and black refrigerant/oil is evacuated from the system, replace the AC compressor. Refer to EPCNet for
applicable part number.
Remedy B - Blockage in the Refrigeration Circuit

1. Identify through SDS function test "Refrigeration circuit test" that the refrigerant circuit has not been underfilled or overfilled.


2. Inspect along the AC lines to check for blockage at the points with marked temperature differences.


3. Identify and replace the blocked components in the refrigeration circuit. Refer to EPCNet for applicable part number.

Remedy C - Electrical Defect in Refrigerant Compressor

1. Identify through SDS function test "Refrigeration circuit test" that the refrigerant circuit has not been underfilled or overfilled.


2. After ruling out a short circuit in the actuation and ground wiring, replace the refrigerant compressor only. Refer to EPCNet for applicable part

number.
Note:
^ Always empty the oil from the new refrigerant compressor before installing.
^ When completely refilling the system, ensure the quantity of oil and refrigerant is correct (refer to WIS document BF83.00-Z-9999AZ). Take
into consideration whether individual components or the entire refrigerant circuit are to be replaced.
^ Always perform a leak test on the system after changing the refrigerant circuit but before filling it with refrigerant.
Note:
The following allowable labor operations should be used when submitting a warranty claim for this repair. This information has been generated on
March 10, 2009. Please refer to Netstar --> Star TekInfo --> Star Time for the most current labor time allowance.
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In Case of Warranty, use the tables above.