1991 Audi 100 Cruise Control Isn't Working

Diagnosing Common Issues with the Cruise Control System in Your 1991 Audi 100 and How to Fix Them

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Reviewed by
Aisha
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 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 1991 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 1991 Audi 100?

To effectively diagnose the non-functioning cruise control in your 1991 Audi 100, start with a methodical approach that emphasizes simplicity. Begin by checking the fuse box for any blown fuses related to the cruise control system, as this is a quick and easy fix that can often resolve the issue. Next, inspect the cruise control switch located 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, typically found under the dashboard or in the engine compartment, for any visible signs of damage or disconnection. It’s also crucial to inspect the vacuum lines connected to the system, as leaks or wear can significantly impact performance. Finally, test the speed sensor to ensure it is accurately relaying information to the cruise control module. By following these steps in order, you can efficiently identify and address the root cause of the cruise control malfunction, making your DIY repair process smoother and more effective.

What are the common problems that could cause the cruise control to stop working in a 1991 Audi 100?

When dealing with a malfunctioning cruise control system in a 1991 Audi 100, it's essential to understand the common problems that could be at play. One of the first areas to check is the cruise control switch, as a faulty switch can prevent the system from engaging or disengaging properly. Additionally, vacuum leaks within the cruise control system can lead to a loss of pressure, which is critical for the system's operation. Another potential culprit is the speed sensor; if it is defective, it can disrupt the communication necessary for the cruise control to function correctly. It's also wise to inspect the fuses, as a blown fuse can completely disable the cruise control system. Furthermore, issues with the brake light switch can prevent activation, since the system is designed to disengage when the brake pedal is pressed. Lastly, don't overlook the throttle cable; if it is frayed or stretched, it can hinder the cruise control's ability to maintain a constant speed. By systematically checking these components, you can effectively diagnose and resolve the cruise control issues in your Audi 100.

How urgent is it to address the malfunctioning cruise control in a 1991 Audi 100?

When it comes to a malfunctioning cruise control system in a 1991 Audi 100, the urgency of addressing the issue cannot be overstated. A faulty cruise control can lead to unpredictable vehicle behavior, such as sudden acceleration or deceleration, which significantly increases the risk of accidents on the road. This unpredictability not only endangers the driver and passengers but also poses a threat to other road users. Moreover, neglecting to fix the cruise control can exacerbate the problem, potentially leading to more extensive damage to the vehicle's electrical or mechanical systems. This could result in costly repairs down the line, making it imperative to act swiftly. For the safety of everyone involved and to maintain the integrity of your vehicle, it is crucial to have the cruise control system inspected and repaired by a qualified mechanic as soon as possible. Taking prompt action ensures that your Audi 100 remains safe and reliable on the road.

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1991 Audi 100 Cruise Control Issues & Repairs | RepairPal