Models (all model years):
• Models 163, 203, 209, 211 and 220 with M112 engine;
• Models 163, 164, 171, 203, 209, 211, 215, 219, 220, 230 and 251 with M113 engine;
• Models 164, 171, 203, 209, 211 and 251 with M272 engine;
• Models 164, 209, 211, 216, 219, 221 and 251 with M273 engine;
• Models 164 and 251 with M272/273 engine; and
• Models 164, 211 and 251 with OM642 engine.

If you receive customer reports of noises at the refrigerant compressor with the A/C either activated or deactivated, the cause could be a defective belt pulley or belt pulley bearing. The pulley and pulley bearing can be diagnosed and replaced with the compressor still installed in the vehicle by following the procedures below.

1. Locate the noise by duplicating the conditions under which the complaint occurred.

2. If there is also a cooling performance complaint, the noise could be caused by a low refrigerant level. Perform a refrigerant circuit test according to SDS.

3. Before the belt pulley on the refrigerant compressor is replaced, verify that the following components in the belt drive are not the source of the noise and repair as required: alternator, power steering pump, guide pulleys/tensioner pulleys or water pump.

4. If there is an rpm-dependent whining noise present with both A/C on and off, and the noise is caused by the tensioner pulleys, guide pulleys or refrigerant compressor, continue with step 5.

Note: Make sure that the A/C is shut off. On the push-button unit, select “A/C off” then “OFF” to turn the climate system off, then select climate system “ON.” The compressor should now be off.

5. Remove the poly V-­belt from the refrigerant compressor.

6. Install a shorter belt to bypass the compressor. Route the belt as shown in Fig. 1. A short test belt for the OM642 might not be available.

7. Run the engine with the short belt installed. If the noise is still present, check whether the ­tensioner and/or guide pulleys are the source of the noise. Replace as necessary the ­defective ­tensioner and/or guide pulleys.

8. If the noise is no longer present, allow the engine to cool and proceed to step 10.

9. Replace the compressor pulley as follows.

Note: It is not necessary to remove the compressor or evacuate the refrigeration circuit.

10. Remove the pulley V-­belt. Determine if the diameter of the pulley is 100 mm or 110 mm.

11. Raise the vehicle and remove the lower engine compartment paneling.

12. Remove the hub using a socket and a counterhold tool. Use a small magnet to remove the flat washer from the shaft.

Note: There are two versions of the compressor shaft, a 7 mm hex and one with two flats. The shaft with two flats requires the use of a special socket. To loosen the 7 mm hex head, ensure that proper metric tool is used.

To loosen the pulley:
Method A (Preferred): Hold the compressor shaft stationary and turn the drive hub counter clockwise to loosen (see Fig. 2). Turn the hub clockwise to tighten.

Method B: Hold the drive hub stationary and turn the compressor shaft clockwise to loosen. Turn counter-clockwise to tighten.

13. Remove the pulley bearing’s snap ring.

14. Remove the belt pulley from the end of the compressor housing.

Note: Do not apply a pulling force in an axial direction to the refrigerant compressor shaft.

Assemble the rubber dampers into the new pulley the as shown in example A in Figs. 3 and 4. Make note of the direction of the curvature of the rubber dampers and install them over the reinforcing webs in the pulley, not in the spaces between the webs.

15. Install the new belt pulley onto the end of compressor housing. Make sure it’s the same diameter as the original.

16. Install the snap ring for the pulley bearing with its flat side facing the refrigerant compressor. Make sure the snap ring is seated correctly in the groove. Use snap ring pliers with 90° tips that have a minimum reach of 19 mm (0.75”).

17. Install the washer. Make sure it is flat against the shoulder of the shaft.

18. Install the hub so the drive fingers are inserted into the gaps between the ends of the rubber dampers. Screw the hub onto the compressor shaft clockwise and torque to 35 Nm. The hub continues to tighten when in the compressor is in operation.

19. Install the circlip into the belt pulley. Make sure it’s seated in the groove of the pulley.

20. Install a new standard length poly V-­belt. Start the engine and verify correct belt operation.

21. Install lower engine ­paneling.