1991 Mercedes-Benz 500SL Cruise Control Isn't Working

Fixing Cruise Control Issues in 1991 Mercedes-Benz 500SL

Find Repair Location
Reviewed by
Andrew Hajjar
Written by RepairPal Car Genius
Updated January 14, 2025
0%
30% chance it's the
Sensor
0%
25% chance it's the
Control Module
0%
25% chance it's the
Throttle
0%
20% chance it's
Something else
The most common reasons a 1991 Mercedes-Benz 500SL cruise control isn't working are failed control module, sensor or switch issues, or throttle actuation problems.
  • Sensor: A faulty or malfunctioning sensor can lead to incorrect readings, causing issues with engine performance or other systems relying on accurate data.
  • Control Module: A faulty control module can lead to erratic vehicle behavior or failure of various electronic systems due to improper signal processing.
  • Throttle: A faulty throttle body or a defective accelerator pedal position sensor may be causing inconsistent throttle response.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 1991 Mercedes-Benz 500SL cruise control isn't working?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

In the event that a wheel speed sensor fails, the ABS, traction control system (TCS) and manufacturer specific stability control system lights will illuminate, informing the driver that the systems are disabled. The vehicle will be more prone to tire slip, and normal driving patterns may need to be adjusted to correct for the loss of computer control. On older vehicle's, the speedometer can be affected, causing illumination of the check engine light as well.

What are the initial diagnostic steps to troubleshoot the non-functional cruise control in a 1991 Mercedes-Benz 500SL?

When troubleshooting the non-functional cruise control in a 1991 Mercedes-Benz 500SL, it's essential to adopt a systematic diagnostic approach. Begin by checking the fuse box for any blown fuses related to the cruise control system, as this is a straightforward fix that can often resolve the issue. Next, inspect the cruise control switch on the steering wheel to ensure it is operational; a malfunctioning switch can prevent the system from engaging. Following this, examine the cruise control module for any signs of damage or malfunction, as this component is crucial for the system's functionality. Additionally, inspect the vacuum lines for leaks or damage, as these can significantly impact the cruise control's performance. It's also important to test the brake pedal switch, as a faulty switch can inadvertently disable the cruise control. Finally, verify the vehicle speed sensor to ensure it is providing accurate data to the cruise control system. By methodically working through these steps, you can effectively diagnose and address the issues affecting your cruise control system.

What are the common problems that could cause the cruise control to stop working in a 1991 Mercedes-Benz 500SL?

When troubleshooting the cruise control system in a 1991 Mercedes-Benz 500SL, it's important to consider several common problems that may be at play. One of the primary culprits is a failed control module, sensor, or switch, which can disrupt the communication necessary for the cruise control to function. Additionally, issues with the throttle actuation system can significantly impact the performance of the cruise control, as it relies on precise throttle control to maintain speed. Other potential problems include faulty wiring or connections, which can lead to intermittent functionality or complete failure of the system. By systematically checking these components, DIYers can identify the root cause of the issue and take appropriate steps to restore the cruise control to working order.

How urgent is it to address the non-functioning cruise control in a 1991 Mercedes-Benz 500SL?

When it comes to the non-functioning cruise control in a 1991 Mercedes-Benz 500SL, addressing the issue should be a priority for any DIY enthusiast. While it may not pose an immediate safety risk, the convenience of cruise control significantly enhances the driving experience, especially on long trips where maintaining a constant speed can alleviate driver fatigue. Ignoring this feature can lead to frustration during highway drives, where its absence is most felt. Moreover, neglecting the problem could allow underlying issues to escalate, potentially affecting the vehicle's electrical system or other components. Therefore, while it may not be an emergency, timely attention to the cruise control malfunction is advisable to ensure a smoother driving experience and to prevent more serious complications down the road.

You’ve got options with RepairPal

Whether you need a more accurate auto repair estimate or help finding a reputable shop in your area, we’ve got you covered.