What does heating mode look like on my air conditioning controller?

You look at the controller.
You see symbols.
You are not sure what they mean.

This is a common issue during colder months. Many people try to heat their home using air conditioning but never confirm the system is actually in heating mode. The controller gives the answer, but only if you know what to look for.

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Why the controller matters more than the temperature

The controller tells the system what to do.

The temperature sets the target.
The controller mode sets the action.

If the controller is not in heating mode, the system will not heat the room regardless of the temperature shown on screen.

This is why checking the controller display is always the first step.

The most common heating mode indicators

Most air conditioning controllers use simple visual cues.

Heating mode is usually shown by
A sun symbol
The word HEAT
A red or orange colour indicator

Cooling mode is usually shown by
A snowflake symbol
The word COOL
A blue colour indicator

If you do not see a sun or HEAT, heating is not active.

Why symbols vary between systems

Not all controllers look the same.

Wall controllers, handheld remotes, and smart controls use different layouts. Some show text. Others rely only on symbols. Some hide the mode behind menus.

This variation causes confusion, especially when users switch between rooms or properties with different systems.

The principle stays the same.
You must positively identify heating mode.

Where to find the mode on your controller

Look for a button labelled MODE.

Pressing it cycles through available options.
Each press changes how the system behaves.

Common modes shown are
Cooling
Heating
Auto
Fan only
Dry

Stop when you see HEAT or a sun symbol.
Then adjust the temperature.

Why auto mode makes controllers harder to read

Auto mode does not lock the system into heating.

When auto mode is active, the controller may still show a sun or snowflake depending on what the system decides at that moment. This can change during the day without warning.

This leads users to believe heating is active when the system has switched back to cooling.

For winter use, manual heating mode gives clearer control.

Controller displays that cause the most confusion

These situations come up often.

A temperature is shown but no mode symbol is visible
The word AUTO is displayed
The fan icon is visible with no heat symbol
Multiple icons appear at once
The display is dim or partially blank

In these cases, assume heating is not active until confirmed.

How to confirm heating is actually running

After selecting heating mode, wait 3 to 5 minutes.

During this time, airflow may be minimal.
The fan may run slowly.
The air may feel neutral at first.

After the system stabilises, warm air should flow steadily.

If this does not happen, recheck the controller mode.

Why changing the temperature does not confirm heating

Many users raise the temperature to test heating.

This does not confirm the mode.

If the system stays in cooling or auto mode, raising the temperature will not produce heat. It only changes the target number on the display.

Always confirm the mode first.

When the controller is not the real issue

If heating mode is clearly active and the room does not warm after 15 minutes, the issue may sit elsewhere.

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

These need assessment rather than controller changes.

When to seek professional support

Contact a specialist if
Heating mode is confirmed but no warmth appears
The controller shows error codes
The display does not respond
The outdoor unit does not run during heating

Before calling, note the controller type, model number, and what the display shows.

This speeds up diagnosis.

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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