A/C - Compressor/Drive Belt Noise
Date: November 30, 2007Order No.: P-B-83.55/87b
Supersedes: P-B-83.55/87a dated August 7, 2007
Group: 83
Revision History
Revision Date Purpose
b 11/30/07 Model 203.040/740 and Respective Information Added
a 8/7/07 Addtion of Mandatory Tool (Step 13)
- 5/3/07 Initial issue
SUBJECT:
All Model 203, 209, 211 and 220, Equipped with M112 Engine
All Model 171, 203, 209, 211, 215, 219 and 220, Equipped with M113 Engine All Model 203.040/740, Equipped with M271 Engine
All Model 171, 203, 209 and 211 Equipped with M272 Engine
All Model 209, 211, 216, 219 and 221 Equipped with M273 Engine
All Model Years
Replacement of Refrigerant Compressor Belt Pulley Due to Noise Complaints or No Cooling (M271 Engine Only)
If you receive customer reports in the above model vehicles of noises at the refrigerant compressor, 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. 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
^ Water pump
3. 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.
4. In addition, on 203 with engine M271 there may be no cooling due to the torque limiter in the drive hub of the pulley being sheared and the compressor not turning. Follow instructions for no cooling starting with step 25.
5. If there is a whining noise that is RPM-dependant which is present with the air conditioning on or off and is determined to be caused by the tensioner pulleys, guide pulleys or refrigerant compressor, continue with step 6.
Note:
The AC compressor does not turn off immediately when AC Off is selected at the control module. In order to insure the compressor is off, select AC off --> select Climate system off --> select climate system on.
Engines M112/113/272/273
6. Remove the poly-V-belt from the refrigerant compressor.
7. 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 96 92)
^ Engines M272/273 - 20 x 2330 to 2340 mm (A011 997 04 92)
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.
8. 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.
9. If the noise is no longer present, allow the engine to cool and proceed to step 10.
10. Replace the compressor pulley as follows.
Note:
It is not necessary remove the compressor or evacuates the refrigeration circuit.
11. Remove the poly-V-belt. Determine if the diameter of the pulley is 100 or 110 mm.
12. Raise the vehicle and remove the lower engine compartment paneling.
13. Refer to Figure 2 for component number references. Remove the belt pulley circlip (Figure 2, 6). With plastic belt pulleys, it is possible to insert a screwdriver under the circlip (Figure 2, 6) and pry it out of the groove.
14. Remove hub (Figure 2, 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 7 mm hex and one with two flats. The shaft with two flats requires the use of socket W112 589 02 09 00.
To loosen the pulley:
Method A (Preferred): Hold the compressor shaft stationary and turn the drive hub counter clockwise to loosen. 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.
It is not a left hand thread. If the shaft breaks off the compressor should be replaced.
15. Remove snap ring (Figure 2, 4) for pulley bearing.
16. Remove belt pulley (Figure 2, 2) from the end of compressor housing.
Note:
Do not apply a pulling force in an axial direction to the refrigerant compressor shaft.
17. Assemble the rubber dampers (Figure 2, 5) into new pulley the as shown in example A in Figure 3 and Figure 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.
18. Install new belt pulley (Figure 2, 2) onto the end of compressor housing. Make sure it is the same diameter as the original, 100 mm, 110 mm or 120 mm (M271).
19. Install the snap ring (Figure 2, 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").
20. Install washer (Figure 2, 3). Make sure it is flat against the shoulder of the shaft.
21. Install hub (Figure 2, 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.
22. Install circlip (Figure 2, 6) into the belt pulley. Make sure it is seated in the groove of the pulley.
23. Install a new standard length poly-V-belt. Start engine and verify correct belt operation.
24. Install lower engine paneling.
Engine M271
25. Remove induction silencer as per WIS document AR09.41-P-6825T.
26. Remove the poly-V-belt.
No Cooling
27. Inspect the AC compressor to see if the shaft is not turning due to a sheared torque limiter in the drive hub. If the hub has sheared follow replacement instructions from step 13 to 23.
28. The cause of the hub shearing could be a seized alternator pulley freewheel. The alternator pulley needs to be inspected as follows. Pry the plastic cover off the end of the alternator pulley. Insert socket wrench tool W602 589 00 10 00 to hold the shaft from turning. Turn the pulley clockwise and it should lock. Turn the pulley counterclockwise, it should freewheel.
29. If the pulley did not freewheel it needs to be replaced. Use a 17 mm wrench on the end of the socket wrench tool and hold it stationary (allow it to contact the frame/sub frame). Insert M10 socket W601 589 00 10 00 through the center of the socket wrench tool and into the end of the alternator shaft and turn the M10 socket clockwise to remove the pulley (Figure 5).
30. Install new pulley and tighten with the M10 socket counterclockwise to 80 Nm. Use a torque wrench that functions in both directions. Install new plastic cover on end of pulley. It is important to follow loosening and tightening instructions as described.
Note:
A seized alternator pulley freewheel will cause the belt tensioner to oscillate back and forth when the engine is running.
Pulley Noise
31. It is not possible to install a shorter belt to bypass the AC compressor due to belt routing. Use a stethoscope to determine if the AC pulley bearing is the source of the noise.
32. Follow AC pulley replacement instructions from step 13 to 23.
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 30, 2007. Please refer to Netstar --> Star TekInfo --> Star Time for the most current labor time allowance.
In Case of Warranty, use the table.