What H4 Means
WHICH MACHINES THIS APPLIES TO: H4 comes from the TL751 XXLW service manual's error-mode section. It is a code on the electric machines in the TL751 and TLS752 family, where the heating is done by two separate elements rather than one.
WHAT H4 MEANS: the service manual gives H4 as "Two heaters disconnected". It is produced by the machine's own heater-check test, which runs both heaters and the motor and then compares the air temperature before and after. The manual's numbers are what define the code: a rise of "5 C or below" over the test period is read as both heaters being disconnected, while a rise of 20 C or greater is recorded as "OK".
WHY THE MACHINE MEASURES HEAT RATHER THAN CURRENT: the control is not checking whether the elements are electrically continuous. It is checking whether the air actually got hotter. That means H4 can be produced by an element that has failed open, by a supply that is not reaching the elements, and by anything in between the two - a thermal cut-out that has opened, a relay that is not closing, a connection that has burnt away at a terminal.
WHAT AN OWNER SEES BEFORE THE CODE: usually the sign arrives first. Loads come out of long cycles still damp, the drum turns normally and the machine sounds entirely healthy, but there is no warmth in the load and no warmth at the door. That combination - everything running, nothing heating - is what this code describes.
A POINT ABOUT THE US SUPPLY: an electric dryer of this size runs on a 240-volt circuit fed by two supply legs. If one of those legs is lost, at the breaker or at the outlet, the motor and the controls can keep running from the other leg while the heating does not. That is a supply condition rather than a machine problem, and it is worth having checked before parts are considered.
HOW THE MACHINE TELLS YOU: the service manual records that the unit buzzes for ten seconds every ten minutes while an error is indicated, and that the error display goes off when the power is switched off and on.
CLASSIFICATION: problem. The machine keeps tumbling and stops heating, which is why it is easy to mistake for a slow dryer rather than a failure.
Common Causes of H4
- Both heating elements failed open
- Thermal cut-out or overheat protector opened, usually after repeated restricted-airflow trips
- One supply leg of the 240-volt circuit lost at the breaker, the outlet or the cord
- Heater relay on the control board not closing
- Burnt or corroded terminal at an element or in the heater harness
- Temperature sensor reading in a way that suppresses the heat request
🔧 One Safe Check You Can Try
There is no element check here for an owner, and the reason is the voltage rather than the difficulty. What is worth doing is the observation that separates a machine problem from a supply problem, because they present identically. Run a short timed program on high heat and, at the end, feel the load and the inside of the door: no warmth at all, with the drum turning normally, is the picture this code describes. Then look at the breaker panel. On a double-pole breaker for the dryer circuit, a trip on one half can leave the machine apparently working while the heat is gone. If the breaker looks tripped, switch it fully off and back on once at the panel; if it trips again, leave it off and have the circuit looked at rather than resetting it repeatedly. Beyond that, clean the lint filter and check the exhaust duct while the machine is cool, because a badly blocked duct causes repeated thermal cut-out trips and a cut-out that has finally stayed open produces exactly this reading. Everything else - elements, relays, cut-outs, terminals - is on the far side of a panel carrying 240 volts and belongs to a technician.
⚠ Why You Shouldn't Go Further Than That
- The heating elements in this class of dryer are supplied at 240 volts, and their terminals are exposed inside the cabinet, so nothing is opened until the machine is unplugged or switched off at the breaker and confirmed dead.
- The heater-check test that produces this code is entered from a service mode by a button sequence, and running it energizes both heaters and the motor deliberately.
- These machines are heavy and frequently stacked or built in, so reaching the back means disconnecting the supply and moving the machine with help rather than alone.
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.