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The role of a condensate drain in an a/c system is to carry away the water that has condensed on the evaporator to the outside of the vehicle. If the condensate drain tube gets blocked then this can result in water spilling into the inside of the vehicle. If you notice wet carpet in the footwell, misting windscreen, particularly on one side only, in the mornings or a musty smell in the vehicle then ask your service department to check the condensate drain tube.


Using the a/c in the winter is great for de-misting the windscreen and windows. As air is drawn into the system it is cooled and moisture from the air will condense in the evaporator. The dried air is then heated by the heater. This warm dry air is much better than the warm moisture saturated air for absorbing moisture.

Annual maintenance of the a/c system is of paramount importance if you want to avoid costly repairs later. 

All systems lose refrigerant naturally. 

The refrigerant/oil mixture lubricates and cools the compressor. 


Whilst the system will work with a reduced refrigerant charge not only will the compressor be running harder and therefore using more fuel but it will BE running with reduced lubrication and cooling and will therefore overheat and wear prematurely. 

This is the most common cause of compressor breakdown. 

Failure to properly evacuate the system prior to charging is the most common cause of condenser leakage. 

The condenser is attacked by the fluoric acid produced by mixing refrigerant with moisture which, when done properly, is removed during evacuation


Overcharging a system is probably worse than undercharging.  This can cause the refrigerant that should be in vapour form in the suction line to enter the compressor as a liquid. 

As liquids cannot be compressed the compressor valves will be damaged and the compressor rendered useless. 

Do not allow anyone to “top-up” your a/c system. 

The only way to safely charge it is to remove the contents and recharge accurately by weight. 

The specification for most vehicles allows a very fine tolerance – typically around 25 grams.

Pollen filters should be replaced regularly otherwise, as they age, they restrict air flow. 

A blocked filter will cause your blower motor to work harder and can cause it to burn out. 

The blower motor resistor which is normally buried deep in your dash is cooled by the air movement in the blower ducts.  This resistor can burn out with insufficient air movement and can be costly to replace. 

Check your handbook to see what the manufacturer recommends. 

Once a year is about the norm but mileage and your location needs to be considered when deciding.

Run the a/c system at least once a week all year round. If the system is not used then the refrigerant oil that helps to form the compressor drive shaft seal will dry out and the refrigerant gas that is held in under pressure can escape.

See your vehicle handbook regarding this.


The service valve caps that are fitted to your a/c are not just to prevent dust entering the valves. They are the primary seals on the service ports and should be kept screwed tight at all times except during service.

The valves in the service ports often leak slightly and they are commonly the source of the loss of refrigerant in an otherwise gas tight system.

Always make sure that the plastic sealing caps are screwed down finger tight.

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