Heat pump not heating: settings, start-up and defrost
A heating pause is not always a fault. The useful distinction is between behaviour described in the manual and a persistent inability to deliver heat.
Confirm a heating request
Select heating mode and a temperature above the current room reading. Fan mode circulates air without providing heat. On a multi-split, check what other indoor units are requesting: permitted combinations depend on the system. Consult the manual before assuming that a setting is incompatible.
Watch the cycle, not just a few seconds
There may be a delay before warm air starts. Under some conditions the system temporarily interrupts heating to defrost its outdoor unit. Record how long this lasts and whether heating resumes. A short pause and a failure that never recovers are different observations for a technician.
When to request assistance
If heat does not return, an error appears or repeated pauses prevent reasonable comfort, record the model and sequence. Do not remove ice with tools or hot water, or open the outdoor unit. Mention whether cooling works normally in summer: that comparison is useful but cannot identify a failed part on its own.
Choose the next step
Use the symptom page to understand the likely causes. If the cause is still unclear, book a diagnosis before approving a repair.