Common, Comprehensive Air Conditioning Maintenance

Proper and scheduled air conditioning maintenance is essential in making sure that your air conditioning unit will be operational as long as possible. A properly maintained air conditioning unit will cost your less in the long run, and you don’t have to go around, looking for a new unit.

I would like to classify air conditioning maintenance into two categories,

One thing to remember before we proceed further.

”If it ain’t broke, don’t fix it”

This famous quote is so true, for maintaining any equipment. We’ll normally do more harm by “trying” to “fix” a problem that is not there in the first place.

The best bet is, to do some simple checks before undertaking maintenance activities.


Type 1: Air conditioning maintenance by yourself:

List of air conditioning maintenance at user level are,

  • Air conditioner filter maintenance,

  • External cleaning of condenser and evaporator,

  • Tube insulation care,

  • Condensate pan and drain care,

  • Simple damper maintenance,

  • Acidity test,

  • Moisture check,

  • Simple leak detection, and

  • Simple fan and blower diagnostic

Short details,


Air conditioner filter maintenance

  • Frequency of maintenance depends on the location of the conditioned room, and intake air condition.

    Some would suggest a frequency of once a month, some would suggest once in three months.

    The real fact is, there is no fixed frequency. We have to determine the frequency after two or three filter maintenance

  • Maintenance of the filter could be replacing the filter for disposable ones, or washing it for electrostatic filters

    More details on air conditioner filter maintenance


Maintaining the condenser and evaporator

  • Common phenomenon with the evaporator and the condenser are damaged fins.

    This problem is easily identified, and rectified using fin comb

  • External cleaning of the condenser and evaporator may be carried out without involving water or cleaning foam.

    Combination of fin brush and a vacuum cleaner would do the trick quite nicely.

    Use of cleaning foam and water would be the best, but it has to be carried out with the electrical supply isolated, and electrical equipment covered to prevent unnecessary water or cleaning solution ingress


Tube insulation care

This is probably the least problematic area within an air conditioning unit.

A good check would be, to find damaged parts of the insulation, and exposed parts of the vapour return line.

The remedy?

  • Get yourself a synthetic rubber tube insulation, matching with the vapour return line size,

  • Remove the damaged insulation (if any),

  • Cut required length of the insulation, and cover the exposed tube length,

  • Secure the insulation by wrapping the ends, with cable tie, or better still, with insulating tapes


Condensate pan and drain care

Condensate pan and drain care is probably the simplest air conditioning maintenance you can perform, but normally overlooked, creating unwanted moss formation, clogging, and evaporator unit flooding.

Maintenance that you can perform on monthly basis are,

  • Testing the water flow from the pan. Better still, use warm water, mixed with detergent

  • Cleaning any debris and dust from drain inlet to prevent clogging,

    Condensate pan care in air conditioning maintenance

  • Cleaning of condensate pan with detergent and wiping it clean to prevent moss formation,

  • Use of wet and dry vacuum cleaner at the outlet of drain line, to pull out dead insects or remaining water within the line


Simple damper maintenance

A damper in air conditioning system may be operated manually, or automatically, using electrical motor, hydraulic system, or pneumatic system.

These dampers will have,

  • Linkages, and

  • Pivot

Cleaning of these points from dust and debris would prevent seizure of dampers.

Simple spray lubrication may be applied to these points, to prevent squeaking sound. Please make sure to wipe off the excess oil.

This maintenance may be carried out on quarterly intervals.


Acidity test

Is used to check for acidity in the refrigerant, or lubrication oil. This test is extremely important in making sure that the compressor will not fail prematurely, from parts erosion and corrosion.

Acid formation within the system happens due to excessive temperature rise, thus disintegrating the refrigerant into chlorine based, or fluorine based acid.

Normal causes for excessive temperature rise are insufficient lubrication, or insufficient cooling from the return refrigerant vapour.

The test could be performed by attaching a bulb to the vapour line service valve, and analysing the colour change of the litmus element.

Quick acid test kit by Qwik, for air conditioning maintenance. Courtesy of Qwik
Courtesy: Qwik

Such bulb is currently being produced by QwikTM, named QwikCheck.

According to QwikTM, if the result of the test shows red, then the system needs to be flushed from acid, refrigerant needs to be changed, filter dryer replaced, and lubrication oil needs to be replaced.

An orange indication means that the filter dryer needs a replacement, and the system needs to be flushed.


Moisture check

Moisture within an air conditioner system is equally as bad as acids.

Presence of moisture will cause ice formation at the low pressure side of the air conditioner, since the temperature will be lower than water’s freezing temperature.

Clogged refrigerant path will reduce flow of refrigerant, lubrication oil, and cause compressor overheating.

Air conditioners that are completely installed at site will have filter dryer, and sight glass attached. Hence presence of moisture within the system can be detected by formation of moisture at the sight glass.

However, there are air conditioners that are hermetically sealed at the manufacturer’s factory. These units will not have sight glass installed. Examples of hermetically sealed units are window air conditioners and portable air conditioners.

A way to check this is by checking if there is any leak within the system. If there is no leak, then there should be no problem.

Otherwise, repairs need to be carried out, and the system has to be re-sealed hermetically by the manufacturer, or a contractor.


Simple leak detection

Leak of air conditioner tubes will pose the threat of refrigerant loss and finally, no cooling or heating.

There are three famous simple leak detection methods at end user level. The,

  • Soap test

  • Electronic leak detector, and,

  • UV light test

Electronic leak detector is the most widely used method nowadays, with lightweight construction, and accurate pin-pointing of the leak position on the tube, or other air conditioner parts.

Treatment for leaks is either part replacement, or repair by tube soldering, or welding.

More on simple leak detection on this page


Simple fan, blower diagnostic

Please turn off ALL electrical supply to the system before performing this.

Diagnostic for fans and blowers include spinning these, and listening to metal rubbing, or any rough noise.

Feel, if it takes extra effort to spin these. A “rough” feel indicates improper lubrication, or bearing wear.

These problems can be treated by wiping off the previous grease/oil on the motor shaft, and applying with new grease/oil.

If the problems still persist, then bearing replacement is required.

Those are the do-able air conditioning maintenance at the user level.

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Let’s move on to,


Type 2: Air conditioning maintenance by trained personnel:

These air conditioning maintenance activities may be carried out at the user level, but,

  • Possibility of air conditioner system failure is higher,

  • Some would violate the law, especially for handling refrigerant.

    All maintenance with regard major refrigerant handling has only been approved to Environmental Protection Agency (EPA) certified persons.

    However, there are possible checks that user can perform before identifying the need for servicing.

    Some of the checks will only release a very minimal amount of refrigerant into the atmosphere, and do not violate the law

  • Possibility of injury from electrocution is also high, if necessary precautions are not taken

Specialised air conditioning maintenance consists of,

  • Refrigerant superheat or subcooling check,

  • Refrigerant leak detection – skilled,

  • Refrigerant charging,

  • System pump down,

  • System evacuation,


    There is another air conditioning maintenance that is related to pump down, and evacuation.

    This is system purging. Limitation of this maintenance activity lies within the construction of the air conditioning system.

    Air conditioning system with a receiver or a service valve on top of the condenser will allow for system purging from non condensable gases (e.g. air).

    This is performed by system pump down, followed by releasing the gases through the service valve on top of the condenser, or at the compressor’s discharge service valve (if available).

    Alternatively, you can evacuate the system, leak test, and recharge with refrigerant.


  • Compressor lubrication oil maintenance,

    consist of lubrication oil top up, and changing.

    Changing of the lubrication oil is simple.

    1. Evacuate the air conditioning system, take out the compressor,

    2. Remove the old lubrication oil into a pan, fill with correct air conditioner compressor lubrication oil, and quantity

    3. Reassemble the system, evacuate it, and charge with new refrigerant

    Lubrication top up has a similar procedure to changing lubrication oil, but we don’t have to follow step (2).

    Perform step (1). Top up until the correct level (based on compressor’s sight glass), and follow reassembling steps shown in (3).

  • System flushing,

    is essential air conditioning maintenance in removing acid from the system.

    The best way to flush after detecting acid, is,

    1. To evacuate the system,

    2. Remove the compressor and the lubrication oil,

    3. Get yourself a flushing solvent, compatible to your refrigerant. Flush the system, and the compressor,

    4. Blow with air and let it dry,

    5. Change the filter dryer, and lubrication oil,

    6. Reassemble the system, evacuate, and charge with new refrigerant

  • Tube soldering,

  • Contactor checking,

    Can be performed,

    • by listening to low vibration hum, or clicking sound.

      This indicates that there is either inadequate voltage to the contactor during engaged position, OR wear of the contactor's parts.

      If changing the contactor doesn't solve the problem, then you have to modify the circuit to the contactor, such that there will be no voltage drop upon engaging

    • by observing on the operation of the compressor, blower, or fan.

      Continuous running and inability to start might (and normally does) suggest a problem with a stuck contactor.

      Try replacing the contactor and observe if it rectifies the problem

  • Motor capacitor checking

    Air conditioner compressors and large blowers will normally be equipped with start capacitor and run capacitor.

    Performing this air conditioning maintenance is easy. Check,

    • if the capacitors are oily, then replace without second thoughts,

    • if (according to Maintstream Engineering) the measured current, multiplied by 2,650, divided by the measured voltage, is lower than 10% of the design capacitance of the capacitor, then replacing it is the best thing to do.

      Voltage measurement can be performed by a voltmeter.

      Current measurement can be measured by an ampere probe

      Formula used to determine capacitance of a motor capacitor, before changing it

    • if you don't hear second "thud" a few seconds after the first "thud" sound during a compressor of blower start that utilises start capacitor,

      then your start capacitor is most likely defective and needs to be replaced

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General best practices on air conditioning maintenance:

It doesn’t matter, what type of air conditioning system we have, the responsibility of taking care of it lies on the owner, or the user.

The user has to take good care during installation, and proper air conditioning maintenance when in operation.

We have to install it as far as possible from sources of standing water, possible physical impact (e.g. adjacent to a football field), and we have to secure the unit firmly on the base/wall/window.

General care during normal operation includes keeping the unit as clean as possible, as dry as possible, and properly lubricated.

It is not advisable to operate the unit, if you’re occupying a space for less than 10 minutes (e.g. rushing back into the house to get your forgotten presentation material).

Finally, air conditioner maintenance or air conditioning maintenance should not be a complicated, and expensive, set of tasks.

In fact, these tasks will save you bucks in the long run. Get it right, and you’ll be enjoying comfort air for years to come.

Simply put, air conditioning maintenance is all about checking, and correct operation, before rectification.

Remember this,

”If it ain’t broke, don’t fix it”



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