Air conditioning systems that have sat unused through winter frequently develop minor issues that only become apparent on the first hot day of the year — which is exactly when you most need them to work. Here are the five essential checks to carry out before summer to make sure your system is ready.
When to Do This
Late March or April is the ideal time — before the first warm spell but with enough time to arrange a service or repair if something needs attention. Don’t wait until the first heatwave to find out your system has a problem.
Check 1 — Clean the Air Filters
This is the single most impactful thing you can do and takes 10 minutes. The air filter sits behind the front panel of the indoor unit. Open the panel (it clips open on most models), slide out the filter and hold it up to the light. If you cannot see light through it clearly, wash it under warm running water, allow it to dry completely and refit.
A blocked filter in summer causes the unit to work much harder than necessary, reduces cooling output, increases electricity consumption and can cause the evaporator coil to ice up — which stops the unit cooling at all. Clean filters are the single biggest factor in efficient summer operation.
Check 2 — Test the System in Cooling Mode
Switch the system on in cooling mode (snowflake symbol on the remote) and set the temperature to a few degrees below the current room temperature. The system should start cooling within 5-10 minutes. Check that:
- Cold air is blowing from the indoor unit
- The outdoor unit is running (you should hear and feel it operating)
- No error codes are displayed on the indoor unit
- There are no unusual noises from either unit
If the system is blowing air but it is not cold, or if the outdoor unit is not running, there may be a refrigerant or electrical fault that needs investigation before summer.
Check 3 — Clear Around the Outdoor Unit
Winter leaves, seed heads, plant growth and general garden debris can accumulate around the outdoor unit over winter. Check that there is clear space on all sides — at least 30cm — and that nothing is blocking the front discharge grille. Overgrown plants are a surprisingly common cause of reduced cooling performance in summer. A unit whose airflow is obstructed cannot reject heat efficiently.
Also check that the outdoor unit’s fins (the thin metal vanes visible through the grille) are not bent or clogged with debris. You can gently straighten bent fins with a fin comb (available from tool suppliers), but heavy contamination of the fins should be addressed by an engineer at the annual service.
Check 4 — Check the Condensate Drain
Air conditioning produces significant condensation in cooling mode — a typical residential unit produces 1-2 litres of water per hour in hot humid conditions. This water drains away through the condensate drain pipe. Over winter, algae and debris can grow in the drain pipe, causing a partial or complete blockage that results in water dripping from the indoor unit when you first run it in summer.
You can flush the condensate drain by pouring a small amount of diluted bleach (1 part bleach, 10 parts water) into the drain pan access point on the indoor unit. This kills algae growth and flushes any minor blockages. If you are unsure where the drain pan is on your specific unit, this is one of the checks we carry out at the annual service.
Check 5 — Book an Annual Service If Due
If your system has not had a professional service in the last 12 months, booking one before summer is worthwhile. A professional service includes coil cleaning, refrigerant pressure check, electrical connection inspection and a full operational test — addressing anything that the above self-checks cannot reach. A well-serviced system uses less electricity, cools more effectively and is much less likely to fail at the worst possible time.
We typically get very busy with service bookings from May onwards as people discover their systems need attention. Booking in March or April means a shorter wait and the peace of mind of knowing your system is ready before the first hot weather.
Book a Pre-Summer Service
Call 07833 053749 or book online. We cover East Grinstead, Surrey, Sussex and South London. Annual service from £95.