What H4 Means
WHICH MACHINES THIS APPLIES TO: the Asko WL6511XXLW, WL6511XXLT and WL6532 XXL. These sit on a bought-in platform rather than on the Asko WM control, and the H-series belongs to them alone. The same letters appear on other Asko appliances meaning different things - H2 on a TL751 dryer is a drying temperature sensor and H2 on a wine cabinet is a zone humidity sensor - so an H-code is only ever read against the machine it appeared on. The source is the service manual for the model, confirmed from the WL6511XXLW document.
HOW THESE MACHINES REPORT A FAULT: all the indicator lights go out, the code blinks in the display, the buzzer sounds for ten seconds every ten minutes, and the display clears when the machine is switched off and on again. Clearing the display is not the same as clearing the problem.
WHAT H4 MEANS: the service manual gives it as "Overheating", and defines the trigger by a number rather than by a sign: the temperature detected by the washing temperature sensor is 205 degrees Fahrenheit, which is 95 degrees Celsius, or higher. The WL6532 document states the same threshold metric-only, as 95 degrees Celsius.
WHY THAT NUMBER IS THE LINE: 95 degrees Celsius is just below boiling, and it is above anything a wash program is meant to reach. No cycle on these machines calls for water at that temperature, so a reading there is either a heater that is not being switched off or a sensor that has stopped telling the truth. Either way the control stops.
WHAT IS ACTUALLY HAPPENING WHEN IT IS REAL: the heater is meant to cycle under the control of the sensor, holding the water in a band. If the heat is not being switched off when it should be - a relay stuck closed, a control that has lost its reference - the water keeps climbing. That is the condition the threshold is there to catch.
THE OTHER POSSIBILITY: a sensor reading high when the water is not. That produces the same code with nothing actually overheating, and the two are separated by measurement rather than by guessing.
WHY THIS PAGE CARRIES A HIGH SEVERITY: because the machine has reported a measured temperature close to boiling in a sealed tub with a door people open. Whether the reading was real is exactly what has not been established yet, and finding out by running another cycle is the wrong way to do it.
CLASSIFICATION: problem, with a scalding risk if the reading is genuine.
Common Causes of H4
- Heater relay stuck or welded closed, so the heat is never switched off
- Control not switching the heating circuit off at the set temperature
- Washing temperature sensor reading high when the water is not
- Water level too low for the heater to be properly covered
- Wiring or connector problem in the heating control chain
🔧 One Safe Check You Can Try
Stop using the machine and switch it off at the outlet or the breaker, and leave the door shut until it has had time to cool - the code reports water close to boiling, and a door opened on a tub that genuinely is at that temperature releases steam and hot water at face height. Give it a good while rather than a few minutes. Once it is cold, there is one observation worth making and no repair to attempt: note whether the laundry from recent loads has been coming out hotter than usual, or whether anything has been shrinking or being damaged in washes where it should not, because that separates a real overheat from a sensor reading high. Note also whether the code arrives on every program or only on the heated ones, and at what point in the cycle. Write it down before clearing the display, since the display clears on a power cycle. Then leave the machine off until it has been looked at. Do not open the cabinet: the heater, its relay and its wiring sit around a spring-suspended drum at mains potential, and there is nothing an owner can measure that would answer the question anyway.
⚠ Why You Shouldn't Go Further Than That
- The code reports water close to boiling, so the machine is switched off and the door left shut until it has fully cooled; a door opened on a genuinely hot tub releases steam and hot water at face height.
- The heater, its relay and its wiring sit inside the cabinet around a spring-suspended drum at mains potential whenever the machine is connected to power.
- Running another cycle to see whether the reading was real is the one test not to make, because if it was real the same thing happens again.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.