Cruise Control - Set Speed Inaccurate/Surges
90mercedes02TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: July 1990
REF. NO. MBNA 30/2
SUBJECT: CRUISE CONTROL MAINTAINS SPEED 3 TO 4 MPH ABOVE SET SPEED AND/OR SURGES ON LEVEL ROADS MODELS 124,126 AND 201
Cruise control amplifiers, 005 545 05 32, with date codes 26/89 through 51/89, installed in vehicles produced from approximately 7/89 to 1/90, may maintain a speed of 3 to 4 mph above the set speed. In addition, mild surging on level roads may occur.
The cruise control will function normally in every other way. The mild speed increase and possible surge are usually difficult to detect. A faulty rubber gasket for the reference resistor may be the originator of the malfunction.
In case of customer complaints, examine the cruise control amplifier. Units affected have a date code (stamped in ink) between 26/89 and 51/89. In these units, examine the rubber gasket for the reference resistor. The faulty gasket, which does not seal out moisture properly, is colored black. If such a gasket is found, simply replace only the gasket with the improved version, colored gray. Do not disassemble the cruise control amplifier.
Procedure
1. Remove reference resistor from amplifier.
2. Carefully remove black rubber gasket from reference resistor area of amplifier. Do not damage amplifier housing or contacts.
3. Insert new rubber gasket, gray in color, with smooth side up. Use reference resistor as a tool to properly seat the gasket.
4. Inspect reference resistor for corrosion, clean it if necessary.
5. Reinstall reference resistor.
Parts Information
Part Name Part Number
Rubber gasket (gray) for reference resistor Q 4 54 0018
In Case of Warranty
Time Allowance
Operation Number Description Time/Model
02-0820 Inspect Cruise Control Amplifier DateCode and 0.3 hr. /45/46
Replace Gasket for Reference Resistor 0.5 hr. /25/70/82/83
(includes R & R Cover Panel) 84/85/86/88
Damage Code
Code Description
54 618 73 Cruise control amplifier reference resistor, electrical fault