Mercedes Benz C 43 AMG Technical Service Bulletin # S-83_55-87F Date: 090310

Mercedes Benz C 43 AMG Technical Service Bulletin # S-83_55-87F Date: 090310

A/C - Various Compressor Noise With A/C ON

Date: March 10, 2009

Order No.: S-B-83.55/87f

Supersedes: S-B-83.55/87e dated Nov. 20, 2008

Group: 83

Revision History

SUBJECT

Replacement of Refrigerant Compressor Belt Pulley Due to Noise Complaints If you receive customer reports in the above model vehicles of noises

at the refrigerant compressor with air conditioning activated and deactivated, the cause could be a defective belt pulley or belt pulley bearing. The

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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 low refrigerant level, perform a Refrigerant Circuit Test as per SDS

and follow instructions for corrective actions.

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

^ Water pump

4. If there is a whining noise that is RPM-dependant which is present with the air conditioning on AND off and is determined to be caused by the

tensioner pulleys, guide pulleys or refrigerant compressor, continue with step 5.

Note:

Make sure that the AC is SHUT OFF! On the push button unit, select "AC off" then "OFF" to turn the Climate System off, then select climate system

on. The compressor should now be off. To see more details on the various push button units, please refer to the climate book, section 2.1 for each

model.

Engines M112/113/272/273

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

6. Install shorter belt to bypass the compressor. Route belt as shown in Figure 1.

Engines M112/113 - 20 x 2315 to 2325 mm (A011 997 86 92 or A 011 997 96 92)

Engines M272/273 - 20 x 2330 to 2340 mm (A011 997 04 92)

Note:

A short test belt for OM642 is currently not available.

Note:

The belts can be sourced locally or by MB part number. The belts must be purchased to diagnose AC compressor pulley noise and are not to be

submitted on a warranty claim.

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.

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9. Replace the compressor pulley as follows.

Note:

It is not necessary to remove the compressor or evacuate the refrigeration circuit. Refer to WIS document AR83.55-P-7685B

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. Refer to Figure 2 for component number references. Remove the belt pulley circlip (Figure 2, Part 6). With plastic belt pulleys, it is possible to

insert a screwdriver under the circlip (Figure 2, Part 6) and pry it out of the groove.

13. Remove hub (Figure 2, Part 1) using a socket and counter hold tool W112 589 07 40 00. Use a small magnet to remove flat washer from shaft.

Note:

There are two versions of the compressor shaft, a 7mm hex and one with two flats. The shaft with two flats requires the use of socket W112 589 02

09 00. To loosen 7mm hex head, ensure that proper METRIC tool is utilized. To loosen the pulley:

Warning!

It is not a left hand thread!

Method A (Preferred and shown in picture above): Hold the compressor shaft stationary and turn the drive hub counter clockwise to loosen (Figure

3a). 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.

14. Remove snap ring (Figure 2, Part 4) for pulley bearing.

15. Remove belt pulley (Figure 2, Part 2) from the end of compressor housing.

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Note:

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

Components damaged due to improper repair procedures may be subject to debit.

Assemble the rubber dampers (Figure 2, Part 5) into new pulley the as shown in example A in Figure 4 and Figure 5. 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.

16. Install new belt pulley (Figure 2, Part 2) onto the end of compressor housing. Make sure it is the same diameter as the original, 100 mm, 110

mm.

17. Install the snap ring (Figure 2, Part 4) for pulley bearing with its flat side facing the refrigerant compressor. Make sure the snap ring is seated

correctly in the groove.

Note:

Use snap ring pliers with 90?tips that have a minimum reach of 19 mm (0.75").

18. Install washer (Figure 2, Part 3). Make sure it is flat against the shoulder of the shaft.

19. Install hub (Figure 2, Part 1) 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.

20. Install circlip (Figure 2, Part 6) into the belt pulley. Make sure it is seated in the groove of the pulley.

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

22. Install lower engine paneling.

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Special Tools

Parts Information

Note:

The following allowable labor operations should be used when submitting a warranty claim for this repair. This information has been generated on

November 20, 2008. 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 table above.