Cruise control system is a popular driving assistance system that helps the vehicle to maintain a set speed automatically. Depending on the manufacturer, the system is called cruise control or tempostat. The assistance system relieves the driver on the road and is one of the most ordered systems in the car. Find out now everything important about cruise control in the car. Also, how you can detect defective parts yourself and replace them.

How cruise control works in the car

Cruise control has been installed in cars as a driving assistance system since the 1960s. The system, also known as cruise control or tempostat, makes it possible to maintain a certain speed. To do this, the driver does not have to keep his foot on the gas pedal; instead, the cruise control system controls the speed fully automatically. An integrated speed limiter also allows the driver to set the maximum speed. This makes driving much more comfortable for drivers, especially when traveling on the highway.

The driver determines the speed

The cruise control is activated and set as desired by the driver himself. Depending on the vehicle, cruise control is activated via a lever on the steering column or by pressing a button on the steering wheel. In addition, the maximum speed can be selected here using the speed limiter. The maximum distance to the vehicle in front can also be set. If the driver presses a switch or steps on the gas pedal, clutch or brake, the cruise control is deactivated.

Adaptive cruise control regulates the distance

Several decades ago, a practical function was added to cruise control as a driver assistance system. Using sensors at the front of the vehicle, the systems measure the distance to the vehicle in front and adjust the speed accordingly. Known as adaptive cruise control, the system increases comfort in stop-and-go traffic. It also noticeably reduces the driver’s workload on the highway.

Cruise control defective – these are the causes

A cruise control system is made up of a complex system of different components. If one of the components is defective or damaged, the cruise control system no longer functions as intended or fails completely. The causes of the defect can be many and varied. In addition, it makes a difference whether the cruise control is controlled electronically, or whether the cruise control has a mechanical or pneumatic control.

Common causes of defective cruise control:

• Control unit for cruise control is defective
• Defect in parts of the vacuum system
• Switch or cable damaged
• Servomotor for cruise control is defective
• Sensor is damaged or dirty

Cruise control with electronic control

Modern vehicles have a cruise control system that is controlled fully electronically. The system uses existing components such as the electronic accelerator pedal or sensors installed in the vehicle. All data is combined and forwarded in the control unit for the cruise control. With this type of system, a defective control unit or defective sensors are often the cause of a fault. Defective cables and switches also cause the system to fail.

Mechanical or pneumatic cruise control

In older vehicles, it is common to find a cruise control system that was designed to be either mechanical or pneumatic in terms of how it works. With this type of cruise control, the causes of failure can be varied. A defective actuator motor or leaking hoses are equally likely causes of failure in older cruise control systems. As with the electronic version, depending on the vehicle model, a control unit is also installed here, which can also fail.

Defective cruise control – these symptoms occur

Typical symptoms often occur when the cruise control system is defective. For example, the desired speed is often not maintained when the cruise control is defective. As soon as the driver takes his foot off the gas pedal, the speed then decreases despite the cruise control being activated. Other symptoms can also occur if the driver assistance system is defective.

Symptoms when the cruise control system is defective:

• Speed is not maintained
• Speed limiter does not work
• Cruise control cannot be activated
• Speed varies despite cruise control
• Adjustment of speed remains off

Other signs of defective cruise control

A defect in the cruise control system is often manifested by the fact that the system can no longer be activated. Although the driver presses the button on the steering wheel or the lever on the steering column, the cruise control is not activated. In the event of a defect, the speed limiter may fail, which means that the speed limit can no longer be activated and the maximum speed cannot be set. Sometimes the speed fluctuates when the cruise control is defective.

Repair or replacement with suitable spare parts

A defective cruise control system significantly reduces driving comfort. Therefore, it is advisable to repair the cruise control system as soon as possible if it is defective. Spare parts for cruise control systems are readily available second-hand and are usually easy to replace.

Control unit and wiring

A common reason for cruise control failure is a defective control unit. Since the control unit cannot be easily repaired in most cases, it is a good idea to replace it with a spare part. A used control unit for the cruise control is usually cheaper than a repair by a specialist. After loosening a few plugs and screws, the defective part can be easily replaced with the spare part. The wiring should also be checked beforehand.

Cruise control with mechanics or vacuum

In the case of cruise control with mechanical control, components such as the servomotor or its mechanical clutch are often defective. If the cruise control is controlled by vacuum, leaking vacuum hoses are often responsible for the failure in older vehicles. Defective vacuum valves are also a possible cause. The electric motor for the control system can usually be easily replaced. The same applies to the components of the vacuum system.

Cruise control switch or steering column lever

If the cruise control cannot be activated, the cause is often a defective switch or a broken steering column lever. However, a switch on the steering wheel or the lever on the steering column can be replaced, although the effort required varies depending on the vehicle model. Sometimes parts of the steering column trim have to be removed or the steering wheel cover disassembled. After that, the switches can be replaced relatively easily using a plug-in connection.

Retrofitting cruise control in the car

If cruise control is not installed in the car, there is often a desire to retrofit this driver assistance system. Retrofitting is generally possible and feasible. It is helpful if the vehicle in question was offered with cruise control. In this case, only the appropriate parts for cruise control need to be purchased and installed. Retrofitting is particularly inexpensive if used parts are used.

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