How to Service an Outdoor Air Conditioning Unit


10 March 2016
In the third “How To…” article by AC&R service and maintenance experts Advanced Engineering, we provide a two-part step-by-step guide on how to perform the perfect service of an outdoor air conditioning unit.


​Most experienced AC&R service engineers will know what’s required to inspect and service an exterior air conditioning unit, but there are a couple of tips and tricks that might make the work quicker and the benefits last longer.

For example, a significant minority of engineers are still reliant on purely mechanical cleaning, despite the advances in chemical cleaning and preventative treatments.

This article is written as an overview: pulling together all the best advice, guidance and techniques relevant to engineers at all levels, whether they’re new to the job or experienced practitioners.
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First things first: The visual inspection

​Outdoor or exterior A/C units are prone to deterioration from the weather, direct sunlight or atmospheric conditions peculiar to the location (e.g. in coastal areas corrosion is greater due to more saline conditions).

When beginning your visual inspection, check the unit’s mounting brackets (if fitted), then look for corrosion on any anti-vibration (rubber) mounts.

It’s also a good idea to inspect the washer between the bracket and the A/C unit to ensure there’s no wobble or movement.

Then inspect the horizontal surface of the L-shaped bracket between the bracket and the bottom of the A/C unit; verify the bolts are tight and the mounts are not deteriorating or decayed due to atmospheric conditions. Often, if the fit is not quite as snug as it should be, any exposure to sunlight can crack the mount.

Finally, run your finger across the integrity of the brackets to check the welding is sound and strong.

General housekeeping

​It barely needs saying, but remove any rubbish, leaf debris or other contaminants and check nothing has blown in. If fitted, clean the drain pan as it’s likely to be filled with rubbish and leaves.

Internal maintenance: The nitty gritty

Before you remove the access panels, isolate the unit electrically. There should be a local isolate as this is a legal requirement for safety, then gently remove the panels to gain access.

Firstly, visually check the electrical connections and cables, look for deterioration, give them a tug to ensure they’re screwed in tightly and identify any loose connections which can be a fire risk for sparks, or result in a build-up of heat in the connection that could start a fire.

They’re usually either push sticks or screws, so see if you can tighten any by hand or with a screwdriver if necessary.

Next, examine the electrical connections and the condition of the fan and motor, checking for deterioration. Look to see whether any blades are bent or whether debris or a bird has gone through it.

Fans tend to be relatively weak, so if they touch something they may bend or break. The fan itself will usually be bolted to the metal frame so make sure this is nice and tight and the fan is not loose or rattling around.

Leak checking inside the unit

Now move the insulation out of the way and – if you use UV leak formulas – look for the tell-tale glow of any refrigeration leaks using UV trace lamps.

Alternatively, you can use a quick bubble-up leak detector, or one of the recommended TIF electronic sniffers. Have a good check of the accessible joints with your detector (you may need to remove insulation to do this).

Make a visual check of the unit’s insulation while the panels are off to ensure the insulation is secure and replace any if necessary. It’s also a good idea to look at any foam bonded to the casework.
That’s it for Part One: in Part Two of this step-by-step guide we will cover servicing and cleaning the heat exchanger, applying protective coatings to prolong the positive effects of servicing, external leak checking and important final checks, visual inspections and documentation.
If you would like specific advice on maintenance and servicing techniques or products, contact the experts at Advanced Engineering on their support hotline: +44 (0) 1256 460 300 or visit their website or YouTube channel for more cleaning tips and guidance.
Read the previous article 'How to clean evaporator and condenser coils' here. Read Part 2 here.