Cooling
It is one of the most common calls we take across the North-East. The air con is switched on, the fan is blowing and yet the room still feels warm and sticky. Before you assume the unit is broken, it is worth knowing that most cooling problems come down to a handful of causes and a fair few of them you can sort out yourself in ten minutes.
After more than 25 years fitting and servicing systems from Newcastle down to Middlesbrough and across to Carlisle, we have seen every version of this. Here is how to work through it in a sensible order, starting with the things you can check and finishing with the faults that genuinely need an engineer.
The reason a sensible order matters is that it saves you both time and money. There is no point calling an engineer out for a filter you could have rinsed in five minutes, and equally there is no point you poking about inside a unit that has a genuine refrigerant fault. Work from the simple and free towards the technical and, by the time you have run out of your own checks, you will know a great deal more about what is actually wrong. That makes any call you do make to us far quicker to put right because you can tell us what you have already tried.
First, check the obvious settings
This sounds daft but it catches people out constantly. A heat pump air conditioner can heat as well as cool, and it is easy to leave it in the wrong mode. On the handset, look for a snowflake symbol for cooling. If you can see a sun, a water drop or a fan-only icon lit up instead, the unit is doing exactly what it has been told to do, which is not cooling.
Next check the set temperature. If the thermostat is set to 24 degrees and the room is already at 23, the unit has reached target and will idle. Drop the setpoint a couple of degrees and listen for the outdoor unit to kick in. Also make sure the fan is not stuck on its lowest speed, as that will make a correctly working unit feel feeble on a hot day.
It is also worth checking that nobody else has changed anything. In a family home or an office it is remarkable how often one person sets the unit to heating or nudges the schedule and then everyone else wonders why the room is wrong. If there is more than one handset or an app on a phone, make sure they are not quietly fighting each other. We have been called out to a unit that would not cool only to find a second remote in a drawer had put the whole thing into fan-only mode weeks before.
- Mode. Snowflake for cooling, not sun, drop or fan.
- Setpoint. Lower than the current room temperature.
- Fan speed. Turn it up to auto or high while you test.
- Timer and sleep. A sleep or eco programme can quietly raise the target overnight.
Dirty filters are the number one culprit
If the settings are right and the unit still underperforms, the filters are the first thing we would look at and nine times out of ten they are the problem. The mesh filters behind the front flap of a wall unit trap dust, pet hair and kitchen grease. When they clog up, airflow across the indoor coil drops and so does the cooling. The unit works harder, uses more electricity and still cannot shift the heat.
The good news is this is a job for you, not us. Lift the front panel, slide the filters out, and either vacuum them or rinse them under a cool tap and let them dry fully before refitting. Do it monthly through summer if the unit runs a lot. A clean filter can transform a tired-feeling system in minutes and it protects the rest of the unit at the same time.
Switch the unit off before you open it and take a proper look while the filters are out. A healthy indoor coil behind them should look clean, with the thin metal fins evenly spaced. If you can see a grey felt of dust packed across those fins, that is restricting airflow too and it is a sign the unit is overdue a proper service, which is a job for us rather than a tap and a cloth. Never force the fins or spray water into the body of the unit. A gentle filter clean is yours to do, deeper cleaning is ours.
One word of warning. If a room has been struggling for weeks with clogged filters, the coil can occasionally frost over as airflow drops. If you find ice when you open it up, clean the filters, leave the unit off for an hour to let it thaw and then try again. If the ice comes straight back with clean filters, stop there, because that points to a refrigerant or airflow fault that needs an engineer.
Check the outdoor unit can breathe
The box on the wall or ground outside is where your room heat is actually dumped. It needs a clear flow of air over its coil. We regularly turn up to find the outdoor unit buried behind a wheelie bin, smothered by a trellis of ivy or packed with leaves and cobwebs. When the outdoor unit cannot reject heat, the whole system chokes and cooling collapses.
- Clearance. Keep at least a foot of free space around and in front of it.
- Debris. Clear leaves, grass cuttings and litter from the fan grille.
- Planting. Trim back shrubs and avoid letting climbers grow across it.
- Sun. A unit baking in full afternoon sun will struggle more than one in shade.
Switch the system off at the controller before you clear anything near the fan, and never poke anything through the grille. A gentle brush and a tidy-up outside is fine for you to do. Anything involving the fins or the fan itself is best left to an engineer.
Is the room sized for the unit?
Sometimes nothing is faulty at all. The unit is simply too small for the space, or the space has changed. A small wall unit sized for a modest bedroom will never cool a knocked-through lounge diner on a hot day, no matter how clean it is. This is why proper sizing at the design stage matters so much, and why a cheap undersized unit is a false economy.
Think about what has changed since it was fitted. Have you taken a wall down, added a conservatory off the room or turned a spare bedroom into a home office full of computers and screens? Every one of those adds heat the original unit was never sized to handle. If the unit runs flat out all day and only just copes, it is probably working as well as it ever will and the honest answer is more capacity.
The giveaway for an undersized unit is that it does fine on a mild day and falls behind on a hot one. A correctly sized system should reach target and then ease off, cycling gently to hold the room. One that never reaches target on the warmest days, and simply runs continuously without the room coming down, is telling you it has run out of capacity. That is not a fault to repair, it is a sizing mismatch, and the fix is either a larger unit or a second unit to share the load. We would always rather tell you that honestly than sell you a repair that will not help.
Solar gain and open doors
Physics does not care how good your air con is. If a room is drinking in heat faster than the unit can remove it, it will not reach temperature. Two things make an enormous difference here and both are free to manage.
Keep the heat out
Large south or west-facing windows pour heat into a room through the afternoon. Close blinds or curtains on the sunny side before the room heats up, not after. Pulling blinds at two in the afternoon when the room is already roasting is far less effective than shading the glass from late morning. External shading does even more, but even ordinary curtains help a lot.
Shut the doors and windows
We still see units running hard with the patio doors wide open. Air conditioning cools the air in a defined space, so trying to cool the room and the garden at the same time is a losing battle. Keep doors and windows shut while the unit is cooling. If you want fresh air, air the room out early morning when it is cool then close it up before the heat of the day.
When it needs an engineer
If you have cleaned the filters, cleared the outdoor unit, checked the mode and shut the room up and it still will not cool, it is time to call us. Some faults are not DIY and should not be attempted. A few point clearly to a job for a qualified engineer.
- Weak cooling and ice. Frost or ice forming on the indoor coil or the pipework often means low refrigerant or an airflow fault.
- Low refrigerant. If the gas charge is low there is almost always a leak. Topping it up without finding the leak is a false fix and, in the UK, refrigerant handling is regulated work.
- Outdoor fan not spinning. If the indoor unit runs but the outdoor fan or compressor is silent, the system cannot reject heat.
- Error codes. Flashing lights or a code on the display point to a specific fault the handset manual or an engineer can decode.
- Water leaking indoors. A blocked condensate drain can cause dripping and should be sorted before it damages the wall.
Refrigerant work in particular is not something to tackle at home. It needs the right qualifications, the right kit and leak detection, and getting it wrong is both unsafe and against the regulations. A proper service will find the real cause rather than masking it.
How long should cooling take
People sometimes think a unit is faulty when in fact they are simply expecting too much too fast. On a hot afternoon a room that has been baking all day will not drop to a comfortable temperature in two minutes. Give a correctly working system a good twenty to thirty minutes to make a real difference to a warm room, longer if the room is large or has had the sun on it all day.
You can help it along without doing anything technical. Turn the fan up to high or auto while the room comes down, keep the doors shut and the blinds drawn on the sunny side, and resist the urge to keep dropping the setpoint. If the room is steadily getting cooler and fresher over that half hour, the system is working fine and just needed a fair chance. If half an hour passes with no real change at all, that is a different matter and worth looking into.
A quick troubleshooting order
If you remember nothing else, run through it in this sequence and you will solve most cooling complaints yourself. Check the mode is set to cooling and the target is low enough. Clean the filters. Clear the outdoor unit. Shut the doors and windows and shade the glass. Give it a good half hour to respond on a hot day rather than expecting an instant change. If it still will not cool after all that, the fault is likely internal and worth a visit.
Talk to Air Con North
If your air con is struggling and the simple checks have not fixed it, we are happy to take a look. We design, supply, install and maintain cooling for homes and businesses right across the North-East, from Newcastle and Gateshead to Sunderland, Durham, Middlesbrough and Carlisle, and we have been doing it for over 25 years. Call us free on 0800 246 5430 for a no-obligation chat or to book a survey. We will tell you straight whether it is a quick fix, a service job or a sizing issue and what would genuinely make the room comfortable again.
