Air Conditioning Not Heating in Winter
The system cools fine in summer but delivers little or no heat when set to heating mode..
The system cools fine in summer but delivers little or no heat when set to heating mode.
What is actually going on
The system cools fine in summer but delivers little or no heat when set to heating mode.
The realistic causes, in order
A failed four-way reversing valve, which is what switches the system between cooling and heating Defrost cycle problems, so the outdoor coil ices and the system spends its time defrosting instead of heating Low charge, which shows up more obviously in heating mode than cooling
What we test on site
Reversing valve operation and coil temperatures on both sides Defrost sensor readings and cycle behaviour in cold conditions System pressures against the manufacturer's heating-mode data
Safe checks to make with air conditioning that won't heat
- Confirm the remote is genuinely in heat mode and not auto
- Check whether the outdoor unit is heavily iced
- Air conditioning used for heating is a heat pump, and its performance in cold weather depends on correct charge and defrost operation — both need F-Gas certified attention.
Who does the work
- Gas Safe registered engineers — registration 554328
- REFCOM registered for F-Gas refrigerant work
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Get air conditioning that won't heat diagnosed properly
Most heating-mode faults are valve, sensor or charge related and are resolved without replacing the system.
Questions we get asked
Why is air conditioning that won't heat happening on an air conditioning system?
A failed four-way reversing valve, which is what switches the system between cooling and heating
What normally puts air conditioning that won't heat right?
Most heating-mode faults are valve, sensor or charge related and are resolved without replacing the system.
Is it safe to keep using the system with air conditioning that won't heat?
Air conditioning used for heating is a heat pump, and its performance in cold weather depends on correct charge and defrost operation — both need F-Gas certified attention.