How to Fix LG Dishwasher Error Code rE: Relay error on the main control board (Full Guide)

Definition: The LG dishwasher “rE” error code signifies a Relay Error occurring on the main control board (PCB). Specifically, it indicates that the relay responsible for controlling the heating element has failed to engage or disengage correctly, preventing the system from regulating water temperature safely and efficiently during the wash or dry cycles.

If your LG dishwasher is displaying this code, you are likely noticing that the water remains ice-cold throughout the cycle, or perhaps the unit is making an incessant clicking sound without proceeding. You might also find that the dishwasher runs for hours without ever finishing. Do not be alarmed; while this involves the “brain” of your machine, it is a diagnosable issue that can often be resolved with a systematic approach to hardware inspection and safety-first troubleshooting.

Symptoms of a Relay Failure

As a Safety Compliance Officer, I must urge you to monitor these symptoms closely, as they often precede a total electrical failure of the appliance:

• Visual Error Code: The control panel is frozen, and the letters “rE” are flashing prominently.
• Cold Wash Cycles: Upon opening the door mid-cycle, the water is lukewarm or cold, and no steam is present, indicating the heater is not being activated by the relay.
• Extended Cycle Times: The dishwasher “stalls” at the beginning of the wash or dry phase because it is waiting for a temperature increase that never occurs.
• Audible Clicking: You hear a rapid or repetitive clicking sound coming from the door or bottom panel, which is the sound of the relay attempting—and failing—to latch.
• Incomplete Drying: Dishes remain dripping wet at the end of the cycle because the heating element was never triggered.

How to Fix LG Error rE (Step-by-Step)

1. Mandatory Power Isolation:

   WARNING: Never attempt to service a dishwasher while it is connected to power. Electricity and water are a lethal combination. You must unplug the unit from the wall outlet. If the unit is hard-wired, go to your home’s breaker box and switch the dedicated dishwasher circuit to the “OFF” position. Verify power is off by attempting to turn on the display.

2. Perform a Hard System Reset:

   Sometimes the relay is simply “tripped” due to a temporary logic glitch. With the power disconnected, press and hold the START/PAUSE button for 15 seconds to drain any residual energy from the capacitors on the board. Leave the unit unpowered for at least 10 minutes. Restore power and attempt a “Rinse Only” cycle to see if the code clears.

3. Access the Main Control Board (PCB):

   If the reset fails, you must inspect the hardware. Open the dishwasher door and remove the Phillips head screws along the inner perimeter of the door. SAFETY TIP: Hold the outer door panel while removing the last two screws so it doesn’t fall and injure your feet. Carefully separate the outer panel to reveal the control board housing, usually located at the top or bottom of the door.

4. Visual Inspection for Thermal Damage:

   Unsnap the plastic cover of the control board. Examine the board meticulously for any signs of black soot, “burned” smells, or melted plastic around the rectangular relay components. If you see scorching on the board, the relay has suffered a catastrophic failure, and the entire PCB must be replaced to ensure fire safety.

5. Continuity Testing:

   Using your multimeter set to the Ohms (Ω) or Continuity setting, test the terminals of the heater relay. If you are experienced with electronics, you can test the relay’s coil resistance. If the relay shows “Open Loop” (OL) where there should be resistance, or if there is no continuity when the relay should be closed, the component is dead. Most homeowners will find it safer and more reliable to replace the whole board rather than desoldering individual relays.

6. Replacing the PCB:

   If the board is damaged, take a photo of the wire harness connections first to ensure correct re-installation. Carefully disconnect the wire clips using needle-nose pliers—do not pull on the wires themselves. Snap the new board into place, reconnect the harnesses, and reassemble the door panel before restoring power.

• Repair Difficulty: Intermediate (Requires handling electrical components and disassembly).
• Estimated Time: 45 to 90 minutes.
• Required Tools:
  • Phillips #2 Head Screwdriver
  • Digital Multimeter (with continuity settings)
  • Needle-nose Pliers (insulated)
  • Work Gloves (to prevent cuts from sharp metal chassis edges)
• Estimated Cost: $0 (if a reset works) to $120–$180 (if the main PCB requires replacement).

Technical Explanation of the Fault

The “rE” error is not a random glitch; it is a specific failure of the electromechanical switches on your control board. Here is why this happens:

• Relay Contact Welding: The heater relay manages high-amperage current. Over time, the electrical arcing that occurs when the relay closes can “weld” the internal contacts together. If the relay is stuck open, no heat is produced; if stuck closed, the heater stays on dangerously long, triggering a safety shutdown.
• Solder Joint Fatigue (Thermal Cycling): The main control board is subjected to constant heating and cooling. This causes the solder joints connecting the relay to the board to expand and contract. Eventually, “cold solder joints” or microscopic cracks form, breaking the electrical path and causing intermittent “rE” errors.
• Voltage Spikes and Surges: Sensitive PCB components are vulnerable to “dirty power.” A sudden surge in the home’s electrical grid can fry the relay’s coil, rendering it unable to create the magnetic field necessary to move the internal switch.
• Heater Element Feedback: If the heating element itself has a partial short or is drawing excessive current, it puts undue stress on the PCB relay. The board detects this abnormal current draw and throws the “rE” code as a protective measure to prevent a fire hazard.

How to Prevent Error rE

To ensure your dishwasher remains compliant with safety standards and to avoid future relay failures, follow these preventative measures:

• Install an Appliance Surge Protector: High-end dishwashers like LG models are essentially computers that wash dishes. Using a dedicated surge protector or a whole-home surge protection system can shield the PCB from voltage spikes that kill relays.
• Ensure Proper Grounding: A loose ground wire can cause electrical “noise” that interferes with relay operation. During your next kitchen inspection, ensure the dishwasher’s electrical box is properly grounded according to local codes.
• Periodic Filter Cleaning: While it seems unrelated, a clogged filter forces the pump and heater to work harder and longer. This puts more “on-time” stress on the heater relay. Keeping the unit clean reduces the total electrical load per cycle.

Frequently Asked Questions

Q: Can I keep using the dishwasher if the rE code only appears occasionally?
A: No. As a safety officer, I strongly advise against this. An intermittent “rE” code indicates a failing relay. If that relay “welds” shut, the heater could stay on indefinitely, potentially melting plastic components or causing a fire. Address the issue immediately.

Q: Is it cheaper to repair the relay or replace the whole board?
A: While desoldering a $5 relay and soldering on a new one is cheaper in parts, it is highly discouraged unless you are a certified electronics technician. A poor solder joint in a high-vibration environment like a dishwasher is a significant fire risk. Replacing the entire manufacturer-certified PCB is the only way to ensure the unit meets original safety specifications.

Q: Does the rE code mean my heating element is broken?
A: Not necessarily. Usually, the “HE” code indicates a heater failure, while “rE” specifically points to the relay on the board. However, a faulty heater can sometimes cause the relay to fail. It is best practice to test the heater for continuity while you have the unit apart.