Error code F15 tells you the washer’s Motor Control Unit (MCU) isn’t doing its job or can’t communicate cleanly with the rest of the system. The MCU powers and monitors the drive motor through the wash and spin phases, taking commands from the Central Control Unit (CCU). When that link breaks or the MCU can’t drive the motor as expected, the machine may tumble weakly, stall during ramp-up, or abort the cycle and post F15.
How the Fault Shows Up
Most machines will lock the door and try to start a wash or spin, then hesitate or surge in short bursts. You might hear the drain pump and relays clicking, but the drum won’t reach stable speed. Sometimes the code appears right at the beginning of a cycle; other times it arrives when the washer tries to transition from slow tumble to medium or high spin. All of these patterns point to the same core problem: the control expects a certain motor response and isn’t getting it.
What Usually Causes F15
Two broad categories create this error: signal/path problems and drive problems. In the first category, harness connectors between the motor, MCU, and CCU loosen, corrode, or seat incorrectly. Even a slightly backed-out pin can interrupt low-voltage data long enough to throw the code. Moisture in the console or at the base can also contaminate terminals, and rough transport can strain harness routing so the cable rubs on the tub or frame. In the second category, the hardware that actually turns the drum can’t deliver: a stretched or slipping drive belt makes the motor work harder and confuses speed feedback; worn brushes or bearings (on motor designs that use them) limit torque; a weak run capacitor on capacitor-start motors allows the motor to start but not sustain speed; and, less commonly, the MCU’s power components overheat or fail and can no longer supply current smoothly.
Safe First Steps and What to Examine
Cut power at the outlet or breaker and give the machine a minute to discharge. With the washer offline, ease the cabinet open and work methodically. Start where failures are most frequent: the harness connections at the MCU, the CCU, and the motor. Reseat each plug until its latch clicks; look for green or white oxidation, heat discoloration, or bent terminal blades. Trace the cable runs and make sure they aren’t pinched under panels or chafing against moving parts. Next, inspect the drive system. Spin the drum by hand; it should turn smoothly and evenly. If you feel gritty resistance or hear scraping, a mechanical issue is loading the motor and will trigger F15 again until corrected. Check belt tension and surface—glazing, frayed edges, or belt dust around the pulley all point to slip. Finally, look over the MCU itself. A faint burnt smell, browned epoxy, or bulged components are red flags that the board’s power stage has failed.
Power Up and Prove the Fix
Once you’ve reseated connectors and addressed anything obvious in the belt path, restore power and run a short cycle or a diagnostic mode. A healthy system locks the door, tumbles with confidence, and ramps to speed without hunting or pulsing. If the code doesn’t return, monitor a full rinse-and-spin to confirm stability. If F15 reappears right away, focus again on the signal path between CCU and MCU; if it appears only when the washer attempts a spin ramp, the motor’s ability to produce torque or the MCU’s ability to supply it remains in question. At that point, a known-good belt and verified harness continuity help isolate the fault to the motor or the MCU. Replacing the belt is quick and inexpensive when slip is suspected; replacing the MCU is the usual next step if the motor tests good yet the control still throws F15 under load.
Prevent a Repeat
Keep the cabinet dry and the rear venting area clear—humidity and leaks shorten electronic life and corrode terminals. Avoid chronic overloading; heavy, unbalanced loads force the motor to hunt and stress both the belt and the MCU. After any move or installation, verify the harness anchors are clipped back into place and the belt runs true on both pulleys. A few minutes of careful routing and inspection now will save you from another F15 later.