Bosch SHXM78W55N (800 Series with MyWay) – Drying fan motor failure Repair Guide

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Model: Bosch SHXM78W55N (800 Series with MyWay)
Brand: Bosch
Model Number: SHXM78W55N

🔍 Problem Description

Test fan motor; check for blockage; replace fan assembly

📋 What You’ll Need

  • Drying fan assembly
  • Multimeter

    • 🔧 Step-by-Step Repair Instructions

      🔧 Step 1: Test drying fan motor with multimeter

      1. Turn off power to the dishwasher at the circuit breaker, then unplug the unit from the wall outlet behind it (you’ll need to pull the dishwasher forward approximately 12 inches to access the outlet).
      2. Remove the lower kickplate by pulling it toward you at the bottom edge – it’s held by 2 spring clips located 8 inches from each side.
      3. Open the dishwasher door and remove all dish racks to access the interior base.
      4. Use a T20 Torx screwdriver to remove the 6 screws securing the sump cover (the circular plastic assembly at the bottom center of the tub).
      5. Lift the sump cover straight up to expose the drying fan motor assembly, which sits on the right side of the sump, appearing as a white cylindrical component approximately 3 inches in diameter.
      6. Locate the drying fan motor wire connector – it’s a 2-pin white rectangular connector with red and black wires, positioned on top of the motor housing.
      7. Press the locking tab on the connector and pull straight up to disconnect it from the motor terminals.
      8. Set your digital multimeter to the ohms (Ω) setting at 200 ohms range.
      9. Touch the red multimeter probe to the terminal with the red wire connection point and the black probe to the terminal with the black wire connection point on the motor itself.
      10. Read the resistance value – a functioning Bosch drying fan motor should show between 180-220 ohms of resistance.
      11. If the reading shows “OL” (open line) or infinite resistance, the motor winding is broken and the motor requires replacement (part number 00755320).
      12. If the reading shows 0 ohms or near zero, the motor winding is shorted and requires replacement.
      13. A reading within the 180-220 ohm range indicates the motor windings are intact and functioning correctly.

      🛠️ Step 2: Check fan for blockages

      1. Locate the circulation fan housing on the left side of the dishwasher interior, directly behind the lower spray arm assembly.
      2. Remove the lower spray arm by lifting it straight up off the mounting hub – it should release without tools.
      3. Remove the spray arm support by turning it counterclockwise one-quarter turn, then lift it straight out of the sump area.
      4. Locate the cylindrical filter assembly in the center of the dishwasher floor and twist it counterclockwise to unlock it.
      5. Lift the filter assembly straight up and set it aside – you’ll see the sump opening beneath.
      6. Look into the sump opening with a flashlight and identify the white or gray plastic fan blade assembly approximately 3 inches down.
      7. Reach into the sump with your fingers and manually rotate the fan blade clockwise – it should spin freely with minimal resistance.
      8. If the fan doesn’t spin freely, remove any visible debris such as bone fragments, toothpicks, glass shards, or food particles lodged between the blades.
      9. Use needle-nose pliers to extract debris you cannot reach with your fingers, gripping items firmly and pulling straight up.
      10. Check the four gaps between the fan blades and the housing walls – common blockage points where small items wedge themselves.
      11. Run your finger around the circular perimeter of the fan housing to feel for buildup of hard water deposits or grease that may restrict movement.
      12. Once clear, spin the fan blade again – you should achieve at least 5 complete rotations from one light push, indicating no blockage.
      13. Shine your flashlight at an angle to inspect the bottom of the fan blade for any objects underneath that might prevent proper seating.
      14. Replace the filter assembly by aligning the arrows on the filter with the arrows in the sump, then twist clockwise until it locks.
      15. Reinstall the spray arm support and lower spray arm in reverse order of removal.

      ⚙️ Step 3: Inspect fan blades for damage

      1. Locate the circulation fan assembly, which is positioned in the left rear corner of the dishwasher tub when facing the open door, approximately 4 inches from the bottom and 3 inches from the left sidewall.
      2. Grip the fan blade housing (a gray plastic cylindrical component measuring approximately 4 inches in diameter) and rotate it counterclockwise one-quarter turn to unlock it from the motor shaft.
      3. Pull the fan blade assembly straight toward you with 5-10 pounds of force to remove it completely from the motor spindle.
      4. Hold the fan blade assembly under a bright light source and examine each of the 6 individual fan blades for these specific defects:
      5. Run your index finger along the leading edge of each blade, moving from the hub outward to the tip. The edges should feel smooth without rough spots or burrs.
      6. Check the central hub (the round plastic piece where all blades connect) for cracks radiating outward from the center mounting hole.
      7. Inspect the mounting hole in the hub center by looking straight through it—the hole should be perfectly round, measuring 8mm in diameter, with no elongation or wear.
      8. Spin the fan blade assembly freely in your hand—it should rotate smoothly without wobbling more than 1-2mm side-to-side.
      9. If you find any cracks, chips, warping, or excessive wobble, the fan blade assembly requires replacement with Bosch part number 00436565.
      10. If the fan blade passes all inspections, set it aside on a clean towel for reinstallation after completing remaining diagnostic steps.

      🔩 Step 4: Test fan operation

      1. Locate the drying fan motor you’ve just installed or serviced—it’s positioned on the left side of the dishwasher tub, approximately 8 inches up from the bottom and 3 inches from the rear wall.
      2. Trace the white 2-wire connector from the fan motor to where it plugs into the main circulation pump housing—this connection point is at the bottom center of the tub, directly below the spray arm assembly.
      3. Verify the connector is fully seated by pressing it firmly until you hear and feel a distinct click—the connector should be flush against the pump housing with no gap visible.
      4. Close the dishwasher door completely until the latch engages with an audible click.
      5. Press the “Power” button on the control panel to turn on the dishwasher.
      6. Press and hold the “Delay Start” button for 5 seconds, then press “Start/Reset” three times within 2 seconds to enter diagnostic mode—the display will show “0:01” if successful.
      7. Press the “>” (right arrow) button repeatedly until the display reads “dF6″—this is the drying fan test mode.
      8. Press the “Start/Reset” button once to activate the fan test cycle.
      9. Listen for the fan motor to start spinning—you should hear a low humming sound approximately 40-50 decibels, similar to a bathroom exhaust fan.
      10. Open the door slowly (the cycle will pause) and place your hand near the left rear vent opening inside the tub where warm air should be flowing—you’ll feel steady airflow if the fan operates correctly.
      11. Close the door and let the test run for 30 seconds, listening for any grinding, squealing, or rattling noises that indicate bearing failure or obstruction.
      12. Press “Power” to exit diagnostic mode—the display will return to normal and the fan will stop within 3 seconds.
      13. If the fan failed to start or made abnormal noise, disconnect power and recheck the wire connector and mounting screws.

      đź“‹ Step 5: Replace fan assembly if motor fails

      1. Locate the circulation pump/fan assembly mounted on the left side of the dishwasher sump, approximately 8 inches from the front door and 4 inches up from the base pan.
      2. Disconnect the white 4-pin wire connector from the fan motor by pressing the release tab on top and pulling straight outward with 5-8 pounds of force until it separates.
      3. Use a T20 Torx bit to remove the two mounting screws securing the fan assembly bracket – one screw located at the 12 o’clock position and one at the 6 o’clock position of the circular mounting ring.
      4. Rotate the entire fan assembly counterclockwise 45 degrees while applying outward pressure until the three locking tabs (positioned at 2, 6, and 10 o’clock) disengage from the sump housing slots.
      5. Pull the fan assembly straight out approximately 3 inches to clear the sump chamber, tilting the top edge toward you by 20 degrees to navigate past the heating element bracket.
      6. Position the new fan assembly (part number 00651956) at the same 20-degree angle and insert into the sump opening until the rear gasket contacts the housing wall.
      7. Align the three locking tabs with their corresponding slots in the sump housing and rotate clockwise 45 degrees until you hear two distinct clicks indicating full engagement.
      8. Reinstall the two T20 Torx mounting screws, tightening each to finger-tight plus one-quarter turn (approximately 15-18 inch-pounds).
      9. Push the white 4-pin connector onto the motor terminals until you hear an audible click – the connector housing will sit flush against the motor body with no gap visible.
      10. Verify installation by manually spinning the impeller through the sump opening – it should rotate freely with no scraping sounds and complete 3-4 full rotations from a single firm spin.

      đź›’ Recommended Products

      Here are the recommended products for this repair: