Error Code C5

The C5 error code on your AEG, Electrolux, or Quelle-Privileg dishwasher primarily indicates a malfunction with the turbidity sensor (also known as the water clarity sensor). This sensor is crucial for determining the soil level of the wash water, allowing the machine to optimize cycle duration, temperature, and water usage. When C5 appears, the dishwasher cannot accurately read the water quality, leading to cycle failure or inconsistent performance. While the sensor is the most common culprit, the main electronic control unit (ECU) may also be at fault.

Meaning of the C5 Error Code

The C5 error means the electronic control unit has detected an implausible or missing signal from the turbidity sensor. The sensor, typically located in the sump assembly, uses optical technology (LED and photocell) to measure the concentration of particles in the water.

If the main board receives a signal that is permanently high (indicating perfectly clear water) or permanently low (indicating excessively dirty water), or if the signal is nonexistent, the C5 error is triggered because the measurement is outside the expected operational range.

Possible Causes of the C5 Error

• Failed Turbidity Sensor: This is the most frequent cause. The optical components (LED transmitter or photocell receiver) within the sensor have failed, resulting in a complete loss of signal or an erroneous reading.
• Damaged or Corroded Wiring: The cable harness connecting the turbidity sensor to the main control board may be cut, pinched, or corroded, interrupting the crucial communication path. Water leakage or rodent damage can often cause this.
• Extreme Mineral or Grease Buildup: Although less common for a hard fault like C5, significant limescale or heavy grease coating the sensor lens can physically obscure the optical path, mimicking a sensor failure.
• Defective Main Control Board (ECU): The electronics on the main control board that interpret the sensor’s voltage feedback may have failed. If the board cannot properly process the incoming signal, it will register the C5 error, even if the sensor itself is functioning correctly.

Troubleshooting Steps

Attempt the following steps in order. Always ensure the appliance is completely disconnected from power before attempting any physical checks or disassembly.

1. Perform a Power Cycle Reset:

   • Unplug the dishwasher completely from the wall outlet.
   • Wait for a minimum of 5 to 10 minutes to allow any residual voltage in the control board capacitors to dissipate.
   • Plug the dishwasher back in and attempt to run a short test cycle. This often clears transient electronic glitches that cause temporary C5 faults.

2. Inspect the Sump and Filter Area:

   • Open the dishwasher door and remove the coarse and fine filters located at the bottom of the tub.
   • Carefully inspect the sump area below the filters. The turbidity sensor is usually visible here or located just underneath this assembly.
   • Check for significant debris, food particles, or severe grease accumulation that might be directly blocking the sensor window. Clean the area thoroughly.

3. Check for Limescale and Mineral Deposits:

   • If you live in a hard water area, heavy limescale buildup might be coating the sensor. Use a dishwasher cleaner specifically designed to remove scale (e.g., citric acid-based cleaners) and run a maintenance cycle.
   • Note: Ensure the cleaner used is safe for your dishwasher model before running a cycle.

4. Inspect Sensor Connections (Advanced Step):

   • WARNING: This requires accessing internal components and may require pulling the dishwasher out or tipping it. Only proceed if you are comfortable with appliance disassembly.
   • Locate the main wiring connections for the sensor, usually found near the base of the machine or the main pump assembly.
   • Check the wiring harness for signs of fraying, rodent damage, or loose connectors. Secure or repair any damaged wiring.

When to Call a Pro

If the C5 error persists after performing a power cycle reset and cleaning the sump area, the issue requires component testing and replacement. These specific fault sources demand specialized tools and electrical knowledge:

• Component Testing: The turbidity sensor often needs to be checked with a multimeter to verify its resistance or voltage output, a task best handled by a technician.
• Sensor Replacement: Replacing the turbidity sensor usually requires accessing the dishwasher’s underside, removing the main pump or sump assembly, and dealing with water seals, which should be done professionally to prevent leaks.
• Control Board Failure: If diagnostics confirm the main control board is defective, its replacement is an expensive and complex procedure involving high-voltage electronics.

Contact a qualified appliance repair technician or the official customer support line for AEG, Electrolux, or Quelle-Privileg to accurately diagnose and safely replace the faulty sensor or control unit.