1990 Audi 100 Cruise Control Isn't Working

Fixing Cruise Control Issues in Your 1990 Audi 100

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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 1990 Audi 100 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 1990 Audi 100 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.

When the vehicle speed sensor fails or the wiring harness prevents signal transmission, the speedometer is the first thing that will stop functioning properly. This can be an intermittent issue where the speedometer only works occasionally, the speedometer may cease all function, or the speedometer may read erratically or incorrectly. Also, the traction control and anti lock brake warning lights specific to each vehicle may be illuminated, depending on the design of those systems. You may notice the vehicle hesitate to accelerate, cruise control will not function properly, and the vehicle may not shift properly through all of the gears.

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 steps to diagnose the non-functioning cruise control in a 1990 Audi 100?

When diagnosing the non-functioning cruise control in a 1990 Audi 100, it's essential to adopt a methodical diagnostic approach. Begin by checking the fuse associated with the cruise control system, as a blown fuse is a straightforward issue that can easily disrupt functionality. Next, inspect the cruise control switch to ensure it is operational; a malfunctioning switch can prevent the system from engaging. Following this, verify the condition of the vacuum lines, as older vehicles often rely on these for proper cruise control operation. Look for any signs of leaks or damage that could hinder performance. Additionally, examine the speed sensor, which is vital for the cruise control system to function correctly; ensure it is providing accurate readings. Finally, consider using a diagnostic scanner to check for any error codes that may indicate specific problems within the system. By following these steps, you can effectively diagnose and address the issues affecting your Audi's cruise control.

What are the common problems that could cause the cruise control to stop working in a 1990 Audi 100?

When troubleshooting the cruise control system in a 1990 Audi 100, it's essential to understand the common problems that may lead to its failure. One of the primary culprits is a faulty cruise control switch, which can hinder the system's ability to engage or disengage as intended. Additionally, a defective cruise control module can disrupt communication between the switch and the engine, resulting in a non-functional system. Another frequent issue is vacuum leaks, which can compromise the system's pressure and its ability to maintain speed. Furthermore, a malfunctioning speed sensor may prevent the cruise control from accurately detecting the vehicle's speed, causing it to disengage unexpectedly. Lastly, electrical issues, such as blown fuses or wiring problems, can interrupt the power supply to the cruise control system. By identifying and addressing these common issues, DIY enthusiasts can effectively restore the functionality of the cruise control system in their Audi 100.

How urgent is it to address the non-functioning cruise control in a 1990 Audi 100?

When it comes to a non-functioning cruise control in a 1990 Audi 100, the urgency of addressing the issue cannot be overstated. While it may not seem like an immediate emergency, neglecting this problem can lead to significant safety risks and potential damage to the vehicle's electrical system or sensors. A malfunctioning cruise control system can disrupt the overall performance of your car, making it crucial to diagnose and resolve any underlying issues promptly. This is especially important for those who frequently embark on long journeys, where cruise control is a valuable feature for maintaining speed and reducing driver fatigue. By prioritizing the repair of your cruise control, you not only enhance your driving experience but also prevent further complications that could result in costly repairs down the line. Therefore, taking the time to troubleshoot and fix the cruise control system is a wise decision for any DIY enthusiast looking to maintain the safety and efficiency of their Audi 100.

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