Parts Database

AC Maintenance

AC Maintenance & Testing

Arnold's Air_Con_Parts

Is your air conditioning operating correctly?
Is the system leaking / noisy or omitting bad odours?

We provide car and commercial vehicle air conditioning repair, servicing, fault finding and system recharging to the trade and general public.

Regular maintenance of your vehicles air conditioning system should be completed on an annual basis. Due to the porosity of the hoses and the systems components the refrigerant gas can leak slowly from the system at around 10 – 15% per year, making the system less efficient and it can gradually stop working altogether.

If the air conditioning system runs out of refrigerant and the system is not used, seals can dry out and will leak when the system is eventually re-charged which could lead to expensive repairs. Always ensure that you run the system on a regular basis throughout the year, the air conditioning unit pulls moisture out of the air and as such acts as a dehumidifier.

Preventive maintenance of the air conditioning system in your car should ensure longer and trouble free service. We can carry out the follow tests which can help identify potential defects that could lead to premature failure:-

Nitrogen Pressure Test

The molecules of nitrogen are smaller than that of refrigerant and it can be easier in a discharged system to detect a leak with pressurised nitrogen, this may identify simple leaks but not those of a temperature, pressure or operational nature. Using nitrogen for leak detection is also better for the environment as it will not damage the ozone layer.

Vacuum Test

It is recommended that the system has a minimum of 30 minute vacuum time to ensure removal of any air and / or moisture that may have entered the system. Failure to remove this would result in poor or reduced performance or damage to the system and its components. Acid can be produced when refrigerant and moisture come into contact with one another which will corrode the system leading to premature failure of components.


One of the most common causes for air conditioning system to fail is due to insufficient refrigerant. All systems will lose 10-15% of their charge per annum and the system will shut down if the pressure drops below predetermined levels to stop further damage. Running a system with a low refrigerant charge will reduce the efficiency of the engine and increase wear in the compressor due to lack of lubrication. There is no benefit in over charging a system as too much refrigerant can cause damage and reduce system efficiency.

UV Dye – Leak Testing

As and when leaks occurs they can be difficult and time consuming to find and costly to rectify. Whilst nitrogen pressure testing is one method of leak detection another is injecting ultraviolet fluorescent dye in with the oil and refrigerant. If a leak occurs it can be found by shining an ultra violet lamp over all of the components of the system looking for leaking dye mix. This is a cost effective leak detection method.

Electronic leak detectors can be used to ‘sniff’ and pinpoint a leak and are very sensitive and accurate.

Refrigeration Oil / Lubricant

Refrigeration oil is the life blood of the compressor, it has two basic purposes to reduce the friction between the moving parts of the compressor and to help extend the life of the shaft seals. It also helps lubricate the moving parts of the expansion valve and the refrigerant service port valve seats. In addition, oil coats the inside of the flexible hoses and plumbing connections which helps reduce leaks.

It is important to ensure that the correct grade of oil is used with the refrigerant. Lubricants for R-134a A/C systems are commonly available in PAG 46, 100, 150 cSt (International Organization for Standardization (ISO) in Centistokes). Oil viscosity must be thick enough at high temperatures to provide a boundary layer of lubrication between moving parts, but thin enough at low temperatures to flow through the tiny spaces between parts that need lubrication. An important property of refrigeration oil is the characteristic that the oil needs to be soluble with the refrigerant.


The only gas currently approved for modern vehicles is R-134a. Some other gasses supplied via the internet or at hardware stores are available but are not best suited to the system and can be inflammable.  A new refrigerant is planned for all new vehicles, the European Union’s date for changeover is January 1st 2011 and will be R-1234yf. This refrigerant known as hydro-fluoro-olefin (HFO) is close enough to HFC – 134a in key characteristics and R-1234yf has the lowest overall global warming impact.

Only certificated individuals suitably trained are allowed to handle refrigerant.

Evaporator Deodorising

As the air conditioning system pulls moisture from the air it holds it in the form of water in the bottom of the evaporator which then drains to the outside of the vehicle. Some moisture will always be present in the evaporator which is usually housed in the heater plenum of the car. The damp and dark conditions collect pollen, dust and organic particles which over time become a breeding ground for bacteria together with viruses and fungi. When operating the ventilation system initially when a vehicle has been left on a hot day, a foul smell can be detected which can be potentially harmful especially to asthma and hay fever sufferers. Bacterial treatment can be undertaken to clean and condition the surface of the evaporator and the drain tray in order to help prevent reoccurrence.  Changing the pollen filter annually ensures filtered fresh air only enters the cabin area of the vehicle.

Replacement Parts

Replacement parts can be supplied and fitted which include compressors, condensers, receiver / dryers, valves, switches, evaporators, tubes and hoses.



Initial Function Test

  • Compressor operation
  • Check controls
  • Take temperature reading using a digital thermometer
  • Check Drive belts, check condition of all hoses and connections

Vacuum Test

Carry out a full vacuum test for thirty minutes and remove any moisture content and air present in the system.

Nitrogen Pressure Test

Pressurise the A/C system using Oxygen-Free Nitrogen to test for leaks.


Recharge the system with R134a refrigerant to correct levels recommended by the vehicle manufacturer.

Refrigerant Oil

Fresh refrigerant PAG oil is topped up during the refrigerant recharge process. 

Operating Pressure

Operating pressures checked to ensure optimum performance of the system.


Check condition of the condenser including blocked air flow and corroded fins and tubes. 

Fan Operation

Lack of air flow through the condenser will reduce performance and could damage the system due heat and pressure.

Service Ports

Check that the service ports do not leak and that they are fitted with correctly fitting caps.

Fault Diagnosis

Fault finding and electrical testing undertaken as required.