Clock Spring

This procedure replaces the clock spring (spiral cable) assembly in the steering column, which enables electrical connections between the steering wheel controls, airbag, and vehicle systems.

Warnings

Tools required

Parts

• Clock spring assembly × 1 — A2204640918 or equivalent OEM
• Steering wheel bolt (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface with front wheels pointed straight ahead
2. Turn ignition off and remove key
3. Disconnect negative battery terminal and wait minimum 15 minutes for SRS capacitor discharge
4. Set steering wheel lock (if equipped) or use steering wheel holding device to prevent rotation
5. Mark steering wheel position relative to column shaft with paint marker for alignment reference

Procedure

1. 1

   Remove lower steering column covers
   Remove the lower knee bolster panel below the steering column by releasing the clips. Remove the lower and upper steering column plastic covers by removing the Torx screws and gently pulling apart the halves. These covers are secured by clips and screws on each side.
   Torque spec

   Steering Column Covers3 Nm (2 lb-ft)
2. 2

   Remove driver airbag module
   Locate the two Torx bolts on the back side of the steering wheel (accessible through holes on left and right sides). Remove both airbag module bolts. Carefully pull the airbag module straight out from the steering wheel. Disconnect the electrical connector and horn contact from the back of the airbag module. Place airbag module face-up in a safe location away from work area.
   ⚠️Always place removed airbag module face-up on a clean surface. Never place face-down as this can cause deployment if accidentally triggered.
   Torque spec

   Airbag Module Bolts7 Nm (5 lb-ft)
3. 3

   Disconnect steering wheel electrical connections
   Identify and disconnect all electrical connectors behind the steering wheel including multifunction switch connectors, paddle shifter connectors (if equipped), and heating element connector (if equipped). Label or photograph connections for reassembly reference. Remove any cable ties or routing clips securing the wiring harness.
4. 4

   Remove steering wheel
   Mark the exact position of the steering wheel relative to the steering shaft with paint marker on both components. Remove the central steering wheel nut using appropriate socket. Thread a steering wheel puller onto the steering wheel hub and apply even pressure to release the steering wheel from the shaft taper. Remove steering wheel carefully, feeding wiring harness through the center opening.
   ⚠Do not strike the steering wheel or shaft during removal. Use only a proper puller to avoid damage to the column or shaft.
   Torque spec

   Steering Wheel Nut54 Nm (40 lb-ft)
5. 5

   Mark clock spring position
   Before removing the old clock spring, verify it is in the centered position by checking alignment marks on the clock spring housing. If visible, mark the exact rotational position of the clock spring housing relative to the steering column with paint marker. This provides additional reference for correct installation.
   ⚠If the old clock spring alignment marks are not visible or the spring appears damaged, it may have already rotated out of position. Note this condition for proper centering of new unit.
6. 6

   Remove clock spring assembly
   Disconnect all electrical connectors from the clock spring assembly, including the main steering column control module connector. Remove the clock spring mounting screws (typically 3-4 screws around the perimeter). Carefully pull the clock spring assembly straight off the steering column shaft, noting how the wiring routes through the column.
   Torque spec

   Clock Spring Screws4 Nm (3 lb-ft)
7. 7

   Prepare new clock spring
   Remove new clock spring from packaging. Verify the clock spring is in the centered/locked position (most new units come with a locking pin or tape). If not locked, center the clock spring by rotating it fully in one direction until it stops, then rotate back approximately 2.5-3 full turns until the alignment marks or arrows line up. Do NOT remove locking device yet.
   ⚠️Never install a clock spring that is not properly centered. This will cause immediate failure and potential safety system malfunction.
8. 8

   Install new clock spring
   Route the wiring harness through the steering column in the same manner as the original. Align the clock spring assembly onto the steering column shaft, ensuring proper engagement with the column mounting points and that alignment marks (if visible) match the reference marks made during removal. Install the clock spring mounting screws and torque to specification.
   Torque spec

   Clock Spring Screws4 Nm (3 lb-ft)
9. 9

   Connect clock spring electrical connectors
   Reconnect all electrical connectors to the clock spring assembly, ensuring each connector clicks fully into place. Verify connectors match the photographs or labels made during disassembly. Remove the clock spring centering lock pin or tape only after all connections are secure.
10. 10

    Reinstall steering wheel
    Feed the steering wheel wiring harness through the center of the clock spring. Align the steering wheel to the steering shaft using the paint marks made during removal, ensuring wheels remain pointed straight ahead. Press the steering wheel onto the shaft taper, ensuring it seats fully. Install the steering wheel nut and torque to specification.
    ⚠Ensure steering wheel is aligned exactly as marked. Misalignment will cause steering angle sensor errors and ESP/handling control malfunctions.
    Torque spec

    Steering Wheel Nut54 Nm (40 lb-ft)
11. 11

    Reconnect steering wheel electrical connections
    Reconnect all electrical connectors behind the steering wheel in reverse order of removal, including multifunction switches, paddle shifters, and heating elements. Secure wiring harness with new cable ties if original ties were cut. Ensure no wires are pinched or stressed.
12. 12

    Reinstall airbag module
    Connect the airbag electrical connector and horn contact to the back of the airbag module, ensuring both click securely into place. Carefully align the airbag module to the steering wheel, ensuring proper seating. Install both airbag module mounting bolts and torque to specification.
    ⚠️Verify airbag connector is fully seated and locked. Partial connection can cause non-deployment in a crash or inadvertent deployment.
    Torque spec

    Airbag Module Bolts7 Nm (5 lb-ft)
13. 13

    Reinstall steering column covers
    Reinstall the upper and lower steering column plastic covers, ensuring all clips engage properly and wiring is not pinched. Install the cover screws and torque to specification. Reinstall the lower knee bolster panel.
    Torque spec

    Steering Column Covers3 Nm (2 lb-ft)

Reassembly

1. Reconnect negative battery terminal and ensure connection is tight
2. Turn ignition to position II (without starting) and verify all dashboard warning lights illuminate then extinguish normally
3. Test all steering wheel controls including horn, radio controls, cruise control, phone buttons, and paddle shifters (if equipped)
4. Turn steering wheel lock-to-lock slowly while stationary to verify clock spring operates through full range without binding or noise

Verification

• Start engine and verify SRS airbag warning light extinguishes after bulb check (should go out within 3-6 seconds)
• If SRS light remains on, use Mercedes STAR diagnostic tool to read fault codes and clear SRS system faults related to battery disconnection
• Verify steering angle sensor reading is correct using diagnostic tool (should read near 0 degrees with wheels straight)
• Test drive vehicle at low speed and verify all steering wheel controls function properly including multifunction buttons, paddles, and ESP/handling systems respond correctly
• Confirm no abnormal noises from steering column during turning and that steering wheel returns to center properly

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