Troubleshooting Window Wipers on a 2009 Kenworth T800

[MikePhua]

Window wipers are an essential part of vehicle safety, especially for large trucks like the Kenworth T800, which are often driven in various weather conditions. When wiper controls fail, such as when the wipers only work on high speed, it can be frustrating and potentially dangerous. This article provides a detailed guide on troubleshooting and resolving the issue of wipers that only run on high, covering common causes, diagnostic steps, and possible solutions.
Understanding the Wiper System in the Kenworth T800
The window wiper system in the 2009 Kenworth T800, like many modern trucks, uses a combination of electrical components to control the wipers' speed and functionality. The key components include:

• Wiper motor: The motor drives the wiper arms and blades.
  
• Wiper switch: Located on the steering column or dashboard, this switch allows the driver to control the wiper speed (low, high, intermittent).
  
• Relay: A relay is used to control the power supply to the wiper motor, ensuring that the wipers work at the correct speed.
  
• Fuses and wiring: These ensure that electrical power is safely transmitted throughout the system.
  

When there’s an issue with any of these components, it can result in abnormal wiper operation, such as wipers only running on high.
Common Causes of Wipers Running Only on High
There are several potential reasons why the wipers on a 2009 Kenworth T800 might only function on high speed. Understanding the possible causes will help narrow down the issue:
1. Faulty Wiper Switch
One of the most common causes of the wipers running only on high is a malfunctioning wiper switch. The switch may have worn out or developed an internal fault that prevents it from sending the proper signals to adjust the wiper speed.

• Symptoms of a faulty switch: If the wipers only run on high and fail to respond to other speed settings (like low or intermittent), the wiper switch may be stuck in the "high" position or be sending incorrect signals.
  

2. Wiper Relay Problems
The wiper relay is responsible for regulating the power supply to the wiper motor based on the input from the switch. If the relay is faulty, it may cause the wipers to run only on one speed, often high.

• Symptoms of a faulty relay: The wipers may stop working entirely or only run at one speed (high). In some cases, the wipers may not work at all until the relay is replaced.
  

3. Electrical Short or Wiring Issue
Electrical problems, such as a short circuit or damaged wiring, can cause the wipers to malfunction. This can interfere with the signals sent from the wiper switch to the motor and cause the wipers to get stuck on a high-speed setting.

• Symptoms of wiring issues: Flickering lights, sudden stop-start motions of the wipers, or failure to switch between different speeds.
  

4. Wiper Motor Malfunction
While less common, the wiper motor itself can fail in a way that causes the wipers to only run on high. This is typically due to internal wear or damage.

• Symptoms of motor failure: The motor may fail to respond to low or intermittent settings but will still work at high speed, indicating that only part of the motor’s functions are operational.
  

Step-by-Step Troubleshooting Guide
If your Kenworth T800's wipers are stuck on high, follow these troubleshooting steps to identify and resolve the issue.
Step 1: Check the Wiper Switch

• Inspect the switch: Check the wiper switch for any visible signs of wear or damage. Test all settings (intermittent, low, high) and confirm that the switch responds to changes.
  
• Test the switch electrically: Use a multimeter to check the electrical continuity of the switch. If there is no continuity for certain settings, the switch may need to be replaced.
  

Step 2: Inspect the Wiper Relay

• Locate the relay: In the Kenworth T800, the wiper relay is typically located in the fuse box or near the wiper motor. Refer to the owner’s manual for the exact location.
  
• Test the relay: Swap the wiper relay with another relay of the same type from the fuse box to see if the issue persists. If the wipers stop functioning, you’ve likely identified a faulty relay.
  

Step 3: Check for Electrical Shorts or Wiring Issues

• Inspect the wiring: Check all wiring connected to the wiper motor, relay, and switch for signs of damage, corrosion, or loose connections. Pay close attention to areas where the wiring may rub against metal surfaces, which can cause shorts.
  
• Test the circuit: Use a multimeter to test the circuit and ensure that the correct voltage is being delivered to the wiper motor at different speed settings.
  

Step 4: Test the Wiper Motor

• Check the motor operation: If the switch, relay, and wiring are all in good condition, but the wipers still only work on high, the motor may be at fault. Test the motor by applying direct power to it and checking whether it responds to different speeds.
  
• Replace the motor: If the motor fails to respond or operates inconsistently, replacing the motor may be necessary.
  

Preventative Maintenance Tips
To prevent future issues with your wipers, it’s essential to perform regular maintenance and inspections.

• Clean the wiper blades: Dirty or worn wiper blades can cause stress on the motor, leading to potential failures. Regularly clean and replace the blades as needed.
  
• Inspect the electrical system: Periodically inspect the wiring and relays to prevent wear and damage from affecting the wiper system.
  
• Test wiper function regularly: Test the wiper system periodically, especially after maintenance or repairs, to ensure that all settings work as expected.
  

When to Seek Professional Help
If you’ve followed all the troubleshooting steps and the wipers are still malfunctioning, it may be time to consult a professional mechanic. A trained technician can run advanced diagnostics, identify electrical issues, or replace complex components such as the wiper motor or switch.
Conclusion: Ensuring Reliable Wiper Performance
A malfunctioning wiper system can be a major inconvenience for truck drivers, especially in challenging weather conditions. By understanding the common causes of wiper issues and following the troubleshooting steps outlined in this article, Kenworth T800 owners can resolve most problems related to wiper performance. Regular maintenance and timely repairs are key to ensuring that the wipers continue to function safely and reliably for years to come.