Cruise Control - Adding a Relay
91mercedes01
REF. NO. 30/8
TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: January 1991
SUBJECT: JERKING DURING DOWNHILL DRIVING WHILE CRUISE CONTROL IS ENGAGED MODEL 201.028
Mild jerking during downhill driving while the cruise control is engaged may be attributed to the deceleration fuel shut-off cycling on and off.
To check this condition, first verify that the complaint exists, then drive the vehicle downhill with the cruise control switched on and the deceleration shut-off switch (S27/2) disconnected. If jerking no longer can be felt, a relay can be installed to disable the deceleration fuel shut-off during cruise control operation.
Note: Do not leave S27/2 permanently disconnected, or rough idle will result.
Figure 4:
Procedure:
1. Make up a wiring harness as shown in figure 4, using the items listed under Parts Information.
Figure 1:
2. Disconnect and cover negative battery terminal.
3. Remove air cleaner.
4. Mount bracket (1) for relay, part number 123 545 49 40, on wheel housing by drilling 2 holes (5 mm dia.) into the bracket, and 2 holes (3.5 mm dia.) into the wheel housing. Paint the bare metal with zinc dust paint. Fasten bracket with 2 screws (2), part number 007976 004203, (Figure 1).
Figure 2:
Figure 3:
5. Attach bracket (3), part number 102 159 27 40, to accelerator linkage using 2 screws (4), part number 000933 004030 (Figure 2).
6. Connect 8-pole adaptor plug of the shop-made harness (5) between the connector for the cruise control actuator (M16x1) (Figure 3).
7. Route harness (5, Figure 3) and fasten 6-pole connector to bracket at wheel housing (1, Figure 2).
8. Install relay (K12) and protective cover on 6-pole connector (Figure 3).
9. Continue routing of harness (5) to microswitch (S27/2) (Figure 3).
10. Disconnect connector of original wiring harness from microswitch (S27/2) and connect it to 3-pole plug of harness (5). Attach this connection (X33/2) to bracket (3) with cable tie (7) (Figure 3).
11. Connect 3-pole connector of harness (5) to microswitch (S27/2).
12. Check adjustment of cruise control connecting rod, adjust if necessary (see job number 30-561). Verify that throttle linkage operates freely without hanging up.
13. Reinstall air cleaner.
14. Connect negative battery terminal. Check cruise control operation.
Figure 5:
Note: The loose pin-and-socket adaptors must be inserted in 8-pole connector locations 1 through 5.
Parts Information
Qty. Part Name Part Number
1 Deceleration shut-off/cruise control relay (K12) 001 542 61 19
1 Cover for relay (K12) 201 545 12 46
1 Connector housing, 8-pole 009 545 76 28
1 Cover for connector housing, 8-pole 009 545 77 28
1 Connector housing, 6-pole 006 545 80 28
1 Cover for connector housing, 6-pole 019 545 46 28
1 Connector housing, 3-pole 012 545 07 28
1 Plug housing, 3-pole 012 545 65 28
7 Pin-and-socket adaptor, 4 mm diameter 010 545 52 28
4 Pin socket, 4 mm diameter 003 545 26 26
2 Pin socket, 2.5 mm diameter 002 545 99 26
2 Pin, 2.5 mm diameter 012 545 58 28
1 Bracket 102 159 27 40
1 Bracket 123 545 49 40
2 Screw 000933 004030
2 Screw 007976 004203
1 Cable tie 001 997 42 90
0.5 m (20") Cable covering, 6 mm diameter 040621 006200
0.5 m (20") Cable covering, 10 mm diameter 040621 010200
0.2 m (06") Electr. wire, 1 sq.mm (16 AWG), gray local supply
0.5 m (20") Electr. wire, 1 sq.mm (16 AWG), green local supply
0.5 m (20") Electr. wire, 1 sq.mm (16 AWG), white local supply
1.0 m (40") Electr. wire, 1 sq.mm (16 AWG), red local supply
1.0 m (40") Electr. wire, 1 sq.mm (16 AWG), black local supply
In Case of Warranty
Time Allowance
Operation Number Description Time/Model
02-3018 Instal. of Deceleration Shut-Off/Cruise Control Relay 0.8 hr. / 47
Damage Code
Code Description
54601 62 Cruise control amplifier, jerking