It is the hottest week of the year, you switch the system on, and the room stays warm. Before you assume the worst, a good share of the calls we get in a heatwave turn out to be something small. Here is how to tell the five minute fixes from the ones that need an engineer.
In this guide
Start with the obvious
Nobody likes being asked whether it is switched on, but we ask because it works often enough to be worth asking. Check the system is in cooling mode and not fan, dry or heating. Remotes get pressed by accident, and a unit blowing room temperature air at you is doing exactly what fan mode is meant to do.
Check the set temperature too. If the target is higher than the room already is, the system has no reason to do anything. Set it a few degrees below the room and give it a minute. Then check for a tripped breaker at your consumer unit. A trip is a symptom rather than a cause, so if it goes again straight away, stop and call someone.
Things you can safely check yourself
These are all outside the sealed parts of the system. None need tools or certification, and between them they account for a fair number of the faults we are called out to.
- The filters. A filter thick with dust chokes the airflow. The system works hard, the air barely moves, and the room never cools. This is the single most common cause of “it is not cooling like it used to”, and it is free to fix.
- The outdoor unit. It has to dump heat into the outside air, so it needs air moving freely around it. Leaves, bins, bikes, fence panels and enthusiastic shrubs all stop that. Clear a good gap and let it breathe.
- The doors and windows. An open door to the hall means you are cooling the hall, the stairs and the landing. On a hot day that is a losing battle.
- The sun. A south or west facing room with the blinds up is a lot of heat arriving every minute. Shade it and the system stops fighting.
- The batteries in the remote. A remote sending nothing looks identical to a system ignoring you.
Do all of these, then give the system half an hour before you judge it. Pulling a hot room down takes longer than people expect, and the first thirty minutes are the hardest work it does.
How to clean a filter properly
On nearly every wall mounted indoor unit the front panel lifts open by hand with no tools. The filters slide straight out. Vacuum them, or rinse them if the manufacturer allows it, then let them dry completely before refitting. That last part matters: a damp filter in a warm unit is how you get the musty smell people ring us about in September.
If you have pets, thick carpets or a smoker in the house, check them monthly through the season. In a normal home, every month or two during heavy use is plenty.
Stop and call an engineer
Everything above is housekeeping. Everything below is not. If you see any of these, switch the system off and ring someone qualified rather than investigating.
- Ice on the pipework or the indoor unit. Ice on an appliance whose whole job is to be cold sounds harmless. It is not. It usually means restricted airflow or low refrigerant, and running on regardless damages the compressor.
- It runs constantly and never gets there. With clean filters and a clear outdoor unit, low refrigerant is a common culprit. Refrigerant does not get used up, so if it is low, it has leaked.
- Water dripping inside. Usually a blocked condensate drain. Cheap if dealt with, expensive once it has run down a wall for a fortnight.
- New noises. Grinding, screeching or heavy rattling from either unit. A quiet hum is normal, drama is not.
- It trips the electrics. Once may be bad luck. Twice is a fault, and resetting a breaker repeatedly is not a fix.
- A burning or chemical smell. Switch it off at the isolator and ring us.
- An error code on the display. Note it down and quote it when you call. It genuinely speeds things up.
None of that is meant to alarm you. Most of these faults are small and cheap when caught early. The same faults left until the system gives up in August are the ones that turn into a compressor replacement.
Why you must not touch the pipework
This needs saying plainly, because there are videos online that will happily show you otherwise. The refrigerant circuit is sealed, and it is not a DIY job. Working on it without F-Gas certification is illegal, not merely unwise.
Refrigerants are fluorinated greenhouse gases and are regulated for that reason. Installation, servicing, leak checking and decommissioning must be carried out by a certified engineer. That covers connecting or disconnecting pipework, adding refrigerant, and anything sold as a top up kit. It is also why venting refrigerant to the air is an offence rather than an inconvenience.
There are practical reasons on top of the legal ones. The circuit runs at pressure and the gas can cause cold burns. Getting the charge wrong wrecks efficiency. And if an uncertified person has been inside it, your manufacturer warranty is finished.
If a fix involves the refrigerant pipework, it is not a job for a homeowner. That is the law, not our opinion.
What is probably wrong
Assuming the obvious things are ruled out, here is what we usually find, roughly in the order we find it.
- Restricted airflow. Filters, coils, or an outdoor unit hemmed in by something that was not there when the system was installed. It cannot move heat if it cannot move air.
- A refrigerant leak. Slow leaks are the sneaky ones. Performance drops over a couple of seasons, the bill climbs, and nobody notices until a hot week exposes it. The repair is finding and fixing the leak, then recharging correctly.
- Dirty coils. The coils are where heat actually moves. Coat them in dust and the whole system slows down. This is one of the main things a proper service deals with.
- A failing fan or capacitor. If the outdoor fan is not running, heat has nowhere to go, and the room will not cool however well everything else works.
- Sensor or control faults. A thermostat reading the wrong temperature makes the system behave in ways that look baffling from the outside.
- Compressor trouble. The expensive one, and usually the end result of a problem above being ignored for long enough.
It is cooling, it just is not keeping up
This is a different complaint from a broken system, and the answer is often uncomfortable. If a system has never quite managed a room on the hottest days, and nothing is faulty, it is very likely undersized. An undersized unit runs flat out and never arrives. An oversized one blasts the room cold, switches off, and leaves the air clammy. Both come from skipping a survey and guessing from a floor area.
It is also worth being honest about what has changed. Loft conversions, new glazing, a knocked through kitchen diner, a spare room that is now a full time office: all of these change the load on a system sized for something else. Our guide on what size air conditioning unit you need goes through how this is worked out properly.
The myth that costs people most
“It just needs gassing up.” This one comes from car air conditioning, where a slow loss over years is normal. A home system is a sealed circuit and does not consume refrigerant. If it is low, there is a leak, and topping it up without finding that leak means paying for the same gas twice and venting the first lot into the atmosphere. Any company offering a top up without a leak test is telling you something about themselves.
Getting it looked at across Teesside
If you have worked through the safe checks and it is still not cooling, that is the point to call. We are F-Gas registered and we service every make and model, including systems we did not install.
We are a family run business on North Ormsby Road in Middlesbrough covering roughly twenty miles around it: Stockton on Tees, Thornaby, Billingham, Norton, Yarm, Eaglescliffe, Ingleby Barwick, Redcar, Marske, Saltburn, Guisborough, Marton, Hartlepool, Peterlee and Darlington. Homes near the coast at Redcar, Marske and Saltburn take a harder life from salt air, so an annual service matters more there, not less.
Ring us on 01642 680 873 to book a repair or a service, or ask for a free survey if the honest answer turns out to be that the system was never right for the room. We will tell you either way.
