Miele Error F138 signifies a critical activation of the machine’s Waterproof System (WPS). This error occurs when the internal float switch, located in the drip tray at the very base of the appliance, detects the presence of water. This is a safety protocol designed to prevent catastrophic flooding in your home by immediately halting the program and activating the drain pump.
📖 Important: Official Documentation
Incorrect repairs can cause fire or injury. Always verify with the manufacturer’s manual.
As a user, you are likely hearing the drain pump running continuously, even if you try to turn the machine off. The display will flash “F138,” and the machine will refuse to start any new cycles. While this indicates a serious leak detection, do not panic; this guide will walk you through the professional safety protocols required to diagnose and rectify the fault.
Symptoms of Error F138
When the Waterproof System is triggered, the Miele washer enters a “safe mode” to protect the property and the internal electrical components. Watch for these specific indicators:
- Continuous Drainage: The most prominent symptom is the sound of the drain pump running incessantly. The machine is attempting to clear any water out of the drum to minimize the volume of a potential leak.
- Locked Controls: The control panel will become unresponsive. You will be unable to select or start any programs until the safety fault is cleared.
- Visual Error Code: The digital display will explicitly flash “F138” or, on older models, the “Waterproof” LED will illuminate steadily.
- Absence of Drum Movement: Even if water is drained, the motor will not engage, as the system has cut power to high-voltage components to prevent short-circuiting.
- External Moisture: You may (but not always) see water pooling on the floor beneath the front-left or rear of the machine.
The Complete Solution
The Complete Solution: Step-by-Step Recovery
CRITICAL SAFETY WARNING: Before proceeding, you must disconnect the appliance from the power supply. Water and electricity are a lethal combination. Failure to isolate the machine could result in severe electric shock.
- Isolation and Drainage:
Unplug the machine. Locate the emergency drain hose behind the small flap at the bottom left. Drain any remaining water from the drum into a shallow tray. Once empty, unscrew the drain filter to ensure no blockage is causing a backup. - Removing Water from the Base Pan:
The F138 error will not clear until the base tray is dry. You have two options:
A) Tipping Method: With a helper, carefully tilt the machine forward at a 45-degree angle. Have towels ready to catch the water that spills out from underneath.
B) Access Method: Remove the front panel or the rear access plate using your Torx T20 screwdriver to manually sponge out the water. Warning: The unit is heavy; use proper lifting techniques to avoid musculoskeletal injury. - Drying the Float Switch:
Locate the polystyrene float switch in the center of the base tray. Even a small amount of residual moisture can keep the switch engaged. Use a hairdryer on a cool/low setting to thoroughly dry the switch and the surrounding wires. Do not use high heat, as this can melt the plastic components. - Internal Leak Inspection:
With the panels removed, use a flashlight to look for “calcium tracks” (white, chalky lines). These are the fingerprints of a leak. Trace these lines back to their source. Check the door seal for tears and the heating element gaskets for signs of weeping. - Electrical Verification (Optional):
If the tray is bone dry but the error persists, use a multimeter to check the continuity of the float switch. If the switch shows no continuity when the float is down, the microswitch itself has failed and must be replaced. - System Reset and Test Run:
Reassemble the panels, ensuring all screws are tightened to factory specifications to prevent vibration. Plug the unit back in. Perform a “Rinse” cycle while keeping a close eye on the base of the machine with a flashlight. If the error returns, a component is actively leaking under pressure and requires professional replacement.
| Specification | Details |
|---|---|
| Difficulty Level | Intermediate to Advanced (Requires physical handling and tool use) |
| Estimated Time | 60 – 120 Minutes |
| Required Tools | Torx T20 Screwdriver, Multimeter, Shop Vac or High-Absorbency Towels, Flashlight |
| Estimated Repair Cost | $0 (Manual drain/dry) to $150 (Replacement Pump/Hose) |
Detailed Diagnosis: Root Causes
Detailed Diagnosis: Root Causes
Understanding why the F138 error occurs is vital for a permanent fix. The sensor is a simple polystyrene float; if it rises, the circuit breaks, and the alarm sounds. Here are the primary failure points:
1. Excessive Sudsing (Oversudsing)
This is the most common “false positive” leak. If non-HE (High Efficiency) detergent is used, or if an excessive amount is added, the foam can expand beyond the drum. This foam eventually condenses back into water and drips down the sides of the outer tub into the base tray. The sensor cannot distinguish between a burst pipe and detergent overflow.
2. Component Wear and Material Degradation
Miele machines are built for longevity, but rubber components like the door bellows (seal), inlet hoses, or internal circulation pipes eventually succumb to “ozone cracking” or chemical fatigue. A pinhole leak in a pressurized hose will spray water directly into the base tray during the fill or rinse cycle.
3. Drain Pump Assembly Failure
The drain pump utilizes a mechanical seal to prevent water from entering the motor housing. Over years of service, grit and debris can erode this seal. Furthermore, if the drain filter is not seated correctly after cleaning, water will seep from the housing and accumulate in the base pan, triggering the F138 alarm.
4. External Environmental Leaks
Occasionally, the fault is not within the machine. If the external tap connections or the “AquaStop” box (the large plastic block on the inlet hose) are leaking, water can travel down the exterior of the hose and enter the machine’s chassis through the rear entry point.
How to Prevent Error F138
To ensure the continued operational safety of your Miele appliance, adhere to the following maintenance protocols:
- Strict Detergent Compliance: Only use High-Efficiency (HE) detergents. Miele’s own “UltraPhase” or “UltraWhite” detergents are specifically formulated to prevent the oversudsing that often triggers the F138 error. Never exceed the manufacturer’s recommended dosage for your water hardness level.
- Bi-Annual Filter Inspection: Every six months, manually unscrew the drain filter and clean out debris (coins, hairpins, lint). Ensure the O-ring seal is lubricated with a small amount of silicone grease or water before re-inserting to ensure a watertight seal.
- Component Replacement Schedule: Professional safety standards suggest replacing inlet hoses every 5 to 7 years, regardless of visible wear. If your machine is in a laundry room without a floor drain, consider installing an additional leak detection tray with an external shut-off valve.
Frequently Asked Questions
Q: Can I just keep tipping the machine to clear the error?
A: No. Tipping the machine is a diagnostic step, not a repair. If water is entering the base tray, there is a mechanical failure. Ignoring a leak near electrical components like the motor or heater is a significant fire and shock hazard.
Q: My machine is dry, but F138 is still there. Why?
A: This usually indicates that moisture is still trapped inside the microswitch housing or the switch itself has shorted out. It may also indicate a “latched” error in the software that requires the machine to be left unplugged for at least 30 minutes to discharge the capacitors.
Q: Is the F138 error covered under Miele’s warranty?
A: If the error is caused by a manufacturing defect (like a cracked tub or faulty pump), it is typically covered. However, if the error is caused by “User Error” (oversudsing or a blocked filter), it is generally not covered by the standard warranty.