How to Replace the Turbidity Sensor on a Samsung Dishwasher

The turbidity sensor in a Samsung dishwasher measures water clarity during the wash cycle. It uses an infrared LED and photodiode to detect how much food residue is suspended in the circulating water. This reading tells the control board when dishes are clean (clear water) so it can end the wash phase and move to rinse. On Auto or Smart cycles, the turbidity sensor determines the actual cycle duration. When it fails, the Auto cycle either runs excessively long (sensor reads dirty water even when clean) or cuts short leaving dishes unwashed (sensor reads clean water immediately).

This sensor is different from the thermistor (temperature sensor) that monitors water heat. They are separate components in different locations within the sump area.

Before You Start

• Tools needed: Phillips #2 screwdriver, small flathead screwdriver, flashlight, clean cloth
• Parts needed: Samsung turbidity sensor (~$15-$45, model-specific)
• Time required: 20-30 minutes
• Difficulty: Intermediate
• Safety warning: Disconnect power at the circuit breaker. The sensor uses low-voltage signaling but is located near high-voltage heating element connections. Always verify power is off before reaching into the sump area.

How to Confirm the Turbidity Sensor Has Failed

1. Auto cycle runs 3+ hours: If the Auto or Smart cycle used to take 90-120 minutes and now runs 180+ minutes, the sensor may be reading turbid (dirty) water constantly, preventing the board from advancing to the rinse phase.

2. Auto cycle ends in 30-40 minutes with dirty dishes: The sensor reads clear water immediately, telling the board dishes are already clean. The cycle advances to rinse before actual washing has occurred.

3. Normal/Heavy cycles work fine but Auto does not: Since Normal and Heavy cycles use fixed timing (not sensor-dependent), they complete successfully. Only sensor-dependent cycles (Auto, Smart, Express with sensor) are affected. This pattern confirms a sensor issue rather than a general mechanical problem.

4. Visual inspection: The sensor lens (the infrared window) may be coated with grease or mineral scale, blocking the light beam. Cleaning the lens sometimes resolves the issue without replacement.

Step-by-Step Instructions

Step 1: Disconnect Power

Turn off the circuit breaker for the dishwasher.

Step 2: Access the Interior

Open the dishwasher door. Remove the lower dish rack. Remove the lower spray arm by twisting it counterclockwise and lifting straight up. Remove the filter assembly (twist the filter handle counterclockwise and lift out both the coarse and fine mesh filters).

Step 3: Locate the Turbidity Sensor

With the filters removed, look down into the sump area at the bottom of the tub. The turbidity sensor is a small cylindrical component (roughly the size of a large marble) mounted in the sump wall. It has a transparent or translucent lens on the face that contacts the water flow. On Samsung dishwashers, it is typically located near the back-left area of the sump, offset from the drain pump opening. A two-wire connector leads from the sensor up to the main harness.

Step 4: Clean the Sensor Lens (Try This First)

Before replacing, try cleaning the sensor lens. Use a soft cloth with warm water and a drop of dish soap to gently wipe the transparent lens surface. Mineral scale or grease film on the lens mimics turbid water readings. After cleaning, reinstall filters and the spray arm, restore power, and run an Auto cycle with a light load. If the cycle completes in normal time, cleaning resolved the issue and replacement is not needed.

Step 5: Access the Sensor from Below (If Cleaning Did Not Help)

Remove the kick plate (two Phillips screws + two plastic squeeze clips). The turbidity sensor can be accessed from below for easier disconnection. Follow the sensor wires from the sump area down to where they connect to the main harness.

Step 6: Disconnect the Sensor Wiring

Locate the sensor's two-wire connector (either accessible from inside the tub near the sump, or from below via the kick plate opening). Press the locking tab and pull the connector apart.

Step 7: Remove the Old Sensor

The turbidity sensor mounts in the sump wall with one of these methods:

• Twist-lock mount: Rotate the sensor body counterclockwise approximately 30 degrees, then pull it out of the sump wall.
• Clip mount: A plastic retaining clip holds the sensor in a hole in the sump wall. Depress the clip tab with a small flathead screwdriver and push the sensor inward (into the sump) to extract it.
• Screw mount: A single small Phillips screw holds a bracket that secures the sensor.

Once released, pull the sensor out. Note the depth at which it was inserted (how far the lens protruded into the water flow path).

Step 8: Inspect the Mounting Hole

Check the mounting hole for debris or scale. Clean with a damp cloth. Ensure the rubber grommet or O-ring (if present) is in good condition. A leaking sensor mount allows water into the wiring area below the sump.

Step 9: Install the New Sensor

Insert the new sensor into the mounting hole with the lens facing into the sump (into the water flow path). Install at the same depth as the original. Secure with the appropriate method (twist-lock, clip, or screw). The lens must be in direct contact with circulating water during operation for accurate readings.

Step 10: Reconnect the Wiring

Plug the sensor connector back together until the locking tab clicks. Route wires away from heat sources and moving parts.

Step 11: Reassemble the Interior

From inside the tub, reinstall the filter assembly (fine mesh first, then coarse, twist clockwise to lock). Reinstall the lower spray arm (push onto its mount and twist clockwise). Reinstall the lower rack.

Step 12: Test the Repair

Restore power. Run an Auto cycle with a moderate load of lightly soiled dishes. The cycle should complete in 90-120 minutes (normal Auto cycle duration). If it completes in normal time and dishes are clean, the sensor is working correctly.

Step 13: Reinstall the Kick Plate

If you removed the kick plate, reinstall it with screws and clips.

Understanding Samsung Turbidity Sensor Operation

The sensor works by shining an infrared light through the water flowing past its lens. A photodiode on the opposite side measures how much light reaches it:

• Clean water: Most light passes through. Sensor reads high light level. Board determines dishes are clean.
• Dirty water: Food particles scatter and block light. Sensor reads low light level. Board continues washing.
• Failed sensor (open circuit): Board receives no reading. Default behavior varies by model: some run maximum cycle time, others flag an error.
• Failed sensor (constant low reading): Board never sees clean water. Cycle runs indefinitely until timeout safety limit.

When to Call a Professional

• The sensor mount hole in the sump is cracked or damaged, causing leaks
• Auto cycle timing is abnormal even after sensor replacement (control board logic issue)
• You cannot locate the sensor in the sump area (some models mount it in a non-obvious position within the circulation path)
• Multiple sensors are failing simultaneously (power issue or control board)

Cost Comparison: DIY vs Professional

Need Professional Help?

• Dishwasher repair service
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• Dishwasher repair cost guide

FAQ

Q: Is the turbidity sensor the same as the temperature sensor on a Samsung dishwasher? A: No. They are different components. The turbidity sensor measures water clarity (how dirty the water is) using infrared light. The temperature sensor (thermistor) measures water heat using resistance changes. They are both in the sump area but serve completely different functions.

Q: Will a failed turbidity sensor affect Normal or Heavy wash cycles? A: On most Samsung models, Normal and Heavy cycles use fixed timing and do not rely on the turbidity sensor. Only Auto, Smart, and some Express cycles use the sensor to determine cycle duration. If Normal/Heavy work fine but Auto runs too long or too short, the turbidity sensor is the likely cause.

Q: Can I just stop using Auto mode instead of replacing the turbidity sensor? A: Yes, temporarily. Using Normal or Heavy cycles bypasses the sensor entirely. However, a completely failed sensor may also affect water-change timing within cycles on some models. Replacement is recommended for optimal cleaning performance and water efficiency.

Q: How do I clean the Samsung turbidity sensor without removing it? A: Remove the lower rack, spray arm, and filter assembly. Reach into the sump and wipe the sensor lens with a soft cloth dampened with warm soapy water. Use a cotton swab for precise cleaning of the lens face. Rinse by pouring a cup of clean water over the sensor area. This is effective when grease or mineral film is the issue.

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