LG LDT7808SS (QuadWash) – Spray arm motor failure Repair Guide

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Model: LG LDT7808SS (QuadWash)
Brand: LG
Model Number: LDT7808SS

🔍 Problem Description

Test spray arm motor; check for obstructions; replace motor assembly

📋 What You’ll Need

  • Spray arm motor assembly
  • Multimeter

    • 🔧 Step-by-Step Repair Instructions

      🔧 Step 1: Test spray arm motor with multimeter

      1. Turn off the circuit breaker controlling your dishwasher at your home’s electrical panel.
      2. Open the dishwasher door and remove all dish racks by pulling them straight out.
      3. Unscrew the lower spray arm by turning it counterclockwise (it’s a single threaded connection, no tools needed).
      4. Remove the filter assembly by lifting the cylindrical filter straight up, then twisting the flat circular screen counterclockwise and lifting it out.
      5. Locate 8 Torx screws around the perimeter of the round sump cover (the gray plastic disc at the bottom center of the tub). Remove all 8 screws using a T20 Torx bit.
      6. Lift the sump cover straight up to expose the spray arm motor assembly directly below.
      7. Identify the spray arm motor – it’s a cylindrical black component approximately 3 inches in diameter located in the center of the sump housing.
      8. Locate the wire connector on top of the motor – it’s a white plastic connector with 2 wires (one white, one black).
      9. Press the locking tab on the connector and pull straight up to disconnect it from the motor terminals.
      10. Set your digital multimeter to the ohms (Ω) setting at 200 ohms range.
      11. Touch one multimeter probe to each of the 2 metal terminals on top of the motor (not the wire connector, but the motor itself).
      12. Read the resistance value – a functioning spray arm motor will show between 8-12 ohms.
      13. If the multimeter displays “OL” (overload) or infinity, the motor windings are open and the motor has failed.
      14. If the reading shows 0 ohms or near zero, the motor windings are shorted and the motor has failed.
      15. Any reading between 8-12 ohms indicates the motor windings are intact and functional.

      🛠️ Step 2: Check for obstructions in spray arm mechanism

      1. Pull out the lower dish rack completely and set it aside.
      2. Locate the lower spray arm assembly in the center bottom of the tub—it’s a white or gray plastic arm approximately 14 inches in diameter with multiple spray nozzles.
      3. Grasp the spray arm at its center hub and pull straight up—it lifts off without tools, no screws required.
      4. Hold the spray arm under running tap water and look through each of the 12-16 spray holes against a light source to identify blockages.
      5. Insert a straightened paper clip or toothpick into each blocked hole, pushing debris through from the outside to the inside cavity.
      6. Fill your kitchen sink with warm water, submerge the spray arm, and shake it vigorously to dislodge internal debris—you’ll see particles exit through the holes.
      7. Inspect the spray arm mount (the circular fitting remaining in the dishwasher floor) for food particles, broken glass, or standing water.
      8. Use your fingers to remove visible debris from the mount, then wipe clean with a damp cloth.
      9. Spin the cylindrical bearing inside the mount with your finger—it should rotate freely 360 degrees without grinding or catching.
      10. Pull out the upper dish rack to access the ceiling-mounted spray arm.
      11. Locate the white plastic center cap (approximately 1.5 inches diameter) at the spray arm hub.
      12. Turn the center cap counterclockwise one-quarter turn and pull down to release the upper spray arm assembly.
      13. Repeat cleaning steps 4-6 for the upper spray arm, which has 8-12 spray holes.
      14. Snap both spray arms back into position—the lower arm seats with downward pressure; the upper arm cap twists clockwise until it stops and locks.
      15. Manually spin each spray arm—both should rotate freely without wobbling or scraping sounds.

      ⚙️ Step 3: Inspect motor for visible damage

      1. Locate the circulation pump motor assembly, positioned at the bottom center of the tub, directly below the spray arm mounting point.
      2. Shine a flashlight onto the motor housing to illuminate the black cylindrical motor body, approximately 5 inches in diameter and 7 inches tall.
      3. Examine the motor’s electrical connector on the right side of the housing—a white rectangular plug with 6 wires (2 red, 2 black, 1 white, 1 green).
      4. Look for burn marks, melted plastic, or discoloration around the connector pins; brown or black residue indicates electrical arcing or overheating.
      5. Inspect the motor housing for cracks, particularly around the mounting bracket attachment points at the top and bottom of the cylinder.
      6. Check the motor shaft seal at the top center where it enters the pump impeller housing; look for white calcium deposits, rust, or water staining indicating a failed seal.
      7. Rotate the motor shaft by hand using needle-nose pliers on the impeller blades visible through the pump inlet (the circular opening at the top); the shaft should turn smoothly with slight resistance.
      8. Listen and feel for grinding, clicking, or excessive resistance while rotating; smooth rotation with only magnetic cogging (subtle notched feeling) is normal.
      9. Examine the rubber vibration dampeners—four black cylindrical mounts, one at each corner of the motor mounting bracket—for cracking, compression damage, or separation from the metal bracket.
      10. Inspect all visible wiring from the motor connector for 12 inches of run length; look for exposed copper wire, cracked insulation, or wire strands pulled from crimp connectors.
      11. Check the capacitor (if equipped on your motor variant)—a cylindrical component 2 inches tall mounted on the motor side—for bulging top, leaking oil, or rust on the metal casing.
      12. Note any unusual odors; a burnt electrical smell or acrid plastic odor indicates internal motor winding damage not visible externally.

      🔩 Step 4: Test motor operation

      1. Locate the wash motor assembly at the bottom center of the dishwasher tub, directly beneath the pump housing where you completed your installation or repair work.
      2. Identify the motor’s wire harness connector – a white rectangular plug with 5 wires (typically black, white, red, blue, and green) positioned on the right side of the motor casing, approximately 3 inches from the motor mounting flange.
      3. Set your digital multimeter to the resistance (Ω) setting at 200 ohms range.
      4. Touch the black probe to the black wire terminal and the red probe to the white wire terminal in the connector – you should read between 10-15 ohms, indicating motor winding continuity.
      5. Move the red probe to the blue wire terminal while keeping black probe on black wire – reading should show 8-12 ohms for the secondary winding.
      6. Reconnect the wire harness to the motor by pushing the white connector firmly until you hear and feel a distinct click.
      7. Restore power at the circuit breaker and open the dishwasher door.
      8. Press and hold the “Rinse” button for 3 seconds, then press “Start” – this activates the diagnostic mode.
      9. Press “Rinse” button once more to cycle to motor test (display shows “t2” or motor icon on control panel).
      10. Press “Start” button – the motor should spin for 10 seconds, producing a steady humming sound at approximately 1800 RPM without grinding, clicking, or squealing noises.
      11. Observe the spray arm through the open door – it should rotate smoothly counterclockwise at 12-18 rotations per minute during the test cycle.
      12. The motor test will automatically stop after 10 seconds – successful operation means water circulates visibly and motor sound remains consistent throughout the cycle.
      13. Press “Power” button to exit diagnostic mode once testing confirms proper motor function.

      đź“‹ Step 5: Replace spray arm motor assembly if faulty

      1. Locate the spray arm motor assembly at the center bottom of the dishwasher tub, directly beneath where the lower spray arm sits.
      2. Remove the lower spray arm by gripping it firmly and turning counterclockwise 1/4 turn, then lifting straight up to disengage it from the motor shaft.
      3. Unscrew the spray arm support using a Phillips-head screwdriver #2, removing the single center screw that secures the circular support plate.
      4. Lift the spray arm support plate straight up and set it aside.
      5. Locate the filter assembly surrounding the motor housing and twist it counterclockwise to unlock, then lift it out of the tub.
      6. Identify 4 Torx T20 screws arranged in a square pattern around the motor assembly housing, approximately 2 inches from each corner of the square base plate.
      7. Remove all 4 Torx T20 screws and set them aside.
      8. Lift the motor assembly housing upward approximately 3 inches until you can see the white wire harness connector underneath, located on the right side of the motor body.
      9. Press the locking tab on the wire connector and pull the connector straight apart to disconnect the motor from the dishwasher’s electrical system.
      10. Remove the old motor assembly completely from the tub.
      11. Position the new spray arm motor assembly (LG part number 5859DD9001A) into the mounting location, aligning the 4 screw holes with the mounting points in the tub floor.
      12. Reconnect the white wire harness by pushing the connector halves together until you hear an audible click, confirming the connection is secure.
      13. Install the 4 Torx T20 screws, tightening them in a diagonal pattern (front-left, rear-right, front-right, rear-left) to 8-10 inch-pounds.
      14. Reinstall the filter assembly by twisting clockwise until it locks.
      15. Replace the spray arm support plate and secure with the center Phillips screw.
      16. Reinstall the lower spray arm by aligning the center hub with the motor shaft and turning clockwise 1/4 turn until it locks.

      đź›’ Recommended Products

      Here are the recommended products for this repair: