How do I switch my air conditioning from cooling mode to heating mode?

You change the temperature.
Nothing improves.
Cold air keeps coming out.

This is one of the most common air conditioning issues during colder months. The system usually works. The settings do not. Many people adjust the temperature but never change the operating mode. The result feels wrong even though the screen looks right.

Why changing the temperature is not enough

Air conditioning responds to two things.
Mode and temperature.

The temperature sets the target.
The mode tells the system what action to take.

If the system stays in cooling mode, raising the temperature will not produce heat. It will continue trying to cool the room down to the new target.

This is the main reason people think their system is broken.

What cooling mode and heating mode actually do

Cooling mode removes heat from the room.
Heating mode adds heat to the room.

They are opposites.

Air conditioning systems do not guess your intention. They follow the selected mode exactly. If cooling mode stays active from summer, the system will behave like it is still summer.

How to identify the current mode on your controller

Look at the display on your remote or wall controller.

Cooling mode usually shows
A snowflake symbol
The word COOL
A blue indicator

Heating mode usually shows
A sun symbol
The word HEAT
A red or orange indicator

If you see a snowflake, the system is set to cooling. It will not heat the room.

Step by step guide to switching to heating mode

This process usually takes under 1 minute.

Press the MODE button.
Cycle through the available options.
Stop when HEAT or the sun symbol appears.
Set your temperature again.
Wait 3 to 5 minutes.

Most systems pause briefly before heating starts. This is normal.

What should happen after switching modes

Once heating mode is selected, the system will not blow warm air immediately.

During the first few minutes, you may notice
Little or no airflow
Slow fan speed
Neutral or slightly cool air

This protects internal components while the system warms internally.

After this period, warm air should begin to flow steadily.

Why people think heating is not working

Several things cause confusion after switching modes.

Standing too close to the unit
Changing settings repeatedly
Expecting instant heat
Using low fan speed
Leaving auto mode active

These behaviours interrupt the heating cycle and delay results.

Auto mode can undo your changes

Auto mode overrides manual intent.

If auto mode is active, the system can switch back to cooling based on sensor readings. This often happens when sunlight warms part of the room or the system overshoots slightly.

For reliable winter heating, avoid auto mode and use heating mode directly.

Fan speed settings that help heating feel quicker

Fan speed affects how warmth spreads.

Low fan speed feels gentle but warms the room slowly.
Medium or higher fan speeds move warm air faster and balance temperature more evenly.

A useful approach is to start on medium fan speed for 10 minutes, then reduce it once the room warms.

Common mistakes that stop heating from working

These issues appear frequently during winter support calls.

Cooling mode left on from summer
Auto mode selected instead of heating
Fan only mode used by mistake
Timers still active overnight
Multiple controllers controlling one system
Windows or doors open nearby

Checking these resolves most problems without further action.

When switching modes does not solve the issue

If heating mode is selected and the room still does not warm after 15 minutes, the issue may not be the settings.

Possible causes include
Low outdoor temperatures affecting output
System sized mainly for cooling
Sensor placement issues
Restricted airflow from dirty filters

These require assessment rather than further setting changes.

When to seek professional support

Contact a specialist if
Heating mode remains active with no warmth
Error codes appear
The outdoor unit does not run in heating
The system shuts down repeatedly

Before calling, note the model number, controller type, outdoor temperature, and how long the issue has been happening.

This helps resolve the issue faster.

Related guidance

Further residential air conditioning guidance is available at
https://www.climateworks.co.uk/residential-air-conditioning

References

UK Government guidance on heat pump operation
https://www.gov.uk/guidance/heat-pumps-how-they-work

Building Regulations Approved Document L
https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l

ClimateWorks residential support records from installations across Hampshire, Berkshire, Surrey, and Oxfordshire between 2022 and 2025

Author

Dr Julian Carter
Technical and Compliance Director
ClimateWorks

Dr Julian Carter has over 20 years of experience in building services engineering, air conditioning system design, and regulatory compliance. He advises on residential and commercial projects across the UK, covering system selection, installation standards, commissioning, and real world performance.

As Technical and Compliance Director at ClimateWorks, he oversees technical governance, installer training, fault diagnosis, and customer education. His work focuses on reducing user related issues, improving system reliability, and ensuring air conditioning systems perform as intended throughout their service life.

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