Radio - Interference/Noise, Radio and Cassette
87mercedes03TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: March 1987 (supersedes MBNA 82/22) REF. NO. MBNA 82/22a
SUBJECT: ENGINE RPM-DEPENDENT INTERFERENCE NOISE DURING RADIO RECEPTION AND CASSETTE OPERATION MODEL 124.0
NOTE: The part number for the required special 8 mm insulated wire has been added.
The interference noise can be transmitted by induction via the wiring for circuit 30 of the interior harness, routed below the radio chassis.
If removal of the radio chassis from the console, while playing, reduces the interference noise, disconnect the wiring for circuit 30, which is part of the interior harness and install a new specially insulated 8 sq. mm wire along the right headlamp harness. As of chassis end no. 1A-197810, this change is being performed at the factory.
FIGURE 1:
Procedure
1. Disconnect and remove battery.
2. Disconnect 8 sq. mm red wire for circuit 30 from terminal block X35 (Figure 1). Cut off ring connector, insulate and tie back the wire.
3. Remove protective rain cover behind battery.
4. Remove fuse carrier from fuse/ relay box.
5. Remove lower left dash panel next to kick panel.
FIGURE 2:
6. Disconnect 8 sq. mm red wire for circuit 30 from terminal block X4 (Figure 2). Cut off ring connector, insulate, and tie back the wire.
FIGURE 3:
7. Connect new specially insulated 8 sq. mm (8AWG) wire to terminal block X4 with a ring connector. Route new wire through fuse box into component compartment (arrow, Figure 3) and along right headlamp harness to terminal block X35. Connect new specially insulated wire to terminal block X35 with a ring connector, secure wire with cable straps (Figure 3).
8. Reinstall removed parts and test function of radio.
Parts Information
Quantity Part Name
Part
1 Insulated wire, 8 sq. mm
124 540 01 34
Time Allowance
02-8229/82/83
Circuit 30 wiring Harness (supply Voltage), Reroute 1.6 hrs.
02-8230/82/83
Circuit 30 wiring Harness (supply Voltage), Reroute 1.3 hrs.
(with Maint. or Repair work)