AIR-CONDITIONING: How do I know if my air conditioning needs servicing?


Use of A/C whilst having too little refrigerant in the system creates suction pressure that can allow air, and thus moisture, to enter, due to the suction pressure falling to less than barometric pressure. The seal on the compressor shaft is usually a lip seal, made to contain the pressure of the gas and facing the wrong way to contain vacuum. With little refrigerant gas available the compressor can pull the suction pressure below zero into vacuum and thus allow air to enter past the lip seal. The acids thus created attack pipework but as the condenser has the thinnest amount of aluminium (to maximise heat transfer) it is usually this which fails first by leaking.

With a standard manually controlled a/c system you should leave the a/c on all the time, even if not using it to cool the car. You should also turn the system to full cold for ten minutes once a week – even through the winter if you can – in order to circulate refrigerant which contains lubricants for the system and its seals. Then switch to full heat through the same pipes to thoroughly dry them out. This gets rid of any moisture in the ventilation trunking where mould and bacteria might be accumulating.

Climate control systems, where the temperature is set by the operator should be left on all the time, as the a/c will be required to fine tune a reduction in temperature. The vehicle will decide for itself whether to engage the compressor or open the outside flaps and let in the outside air, which at 0 - 3c Celsius will have no moisture content anyway.

Excellent explanation of how a/c works from Railroad in The backroom forum:

Air conditioning works by compressing, condensing and evaporating a refrigerant gas R134a. The gas boils at a very low temperature, -26 degrees Celsius. Under normal operation the compressor compresses the gas against an expansion valve (later in the system). The compressed gas becomes hot and at high pressure which then enters a condenser. Air passes through the condenser which allows some of the heat to be dissipated into the air which in turn causes the gas to condense into a high pressure liquid. The liquid the leaves the condenser and passes through a receiver dryer to allow and moisture which could damage components to be safely collected. The moisture free liquid then passes through a tiny nozzle (expansion valve), on the other side of which is a much bigger space. The liquid then becomes low pressure and subsequently the temperature falls considerably. The low pressure cold liquid passes into the evaporator which is inside the car. Heat from inside the car is drawn to the cold evaporator which then causes the low pressure liquid to evaporate into a low pressure gas, which in turn is drawn back to the compressor where the whole process starts over again.

If you don't run the system for long periods of time the gas will never turn to a liquid. The seals in the system can then dry out and deteriorate, causing the gas to be lost.

Opinions are divided on servicing. Most manufacturers say 3 years from registration or 30,000, then every two years after that. Chrysler recommends every 12 months for the Voyager, and Volkswagen now says every 24 months. Some manufacturers such as SAAB have suffered spates of compressor failures. Aircon specialists looking for business will tell you it needs servicing, preferably by a visit to an air-conditioning system specialist, every year. That way they can keep a record of how much gas is being lost from the system. But the only way to test the gas is to draw some off and lab-test it.

www.airconditioningforcars.co.uk recommends to have the A/C serviced at four years old then every three years thereafter. Leave driers undisturbed for anything up to say 8 or 9 years, but always replace them if the compressor is changed and mostly if there is another component to change, depending on the circumstances and the model involved.

Re-gassing a typical air-conditioning system with R134a refrigerant has now fallen to a cost of around £50 + VAT. A service and a new accumulator/dryer costs around £150 + VAT. Some a/c specialists argue that this needs to be done otherwise the silica gel desiccant in the dryer could break up and circulate through the system, severely damaging it. Refrigeration engineer Keith Wood believes that replacing the accumulator is not necessary and could be responsible for introducing harmful dirt or dust to the system. It should only be replaced if the system has lost gas and needs to be re-gassed. In his opinion the only regular checks should be for leaks. A pool of water under the car is, of course, not the result of a leak but of condensation dripping off the condenser and is entirely normal.

The two main causes of failure are lack of gas (via leaks at the system seals) and component breakdown. Low refrigerant means low lubricant, which is contained in the refrigerant, and this can lead to seals drying out, thus losing even more refrigerant and leading to failure of the compressor. Properly repairing a failed system is a four-figure job.

Older systems used CFC emitting R12 gas. This was outlawed throughout the EC in 2001 and replaced by environmentally friendly R134a by all manufacturers.

However, the EC has issued a Directive that a new refrigerant: HFO 1234YF must now be used and has got into a fight with Mercedes Benz that claims that the new gas is more flammable.

Some manufacturers such as Peugeot in the 308 and Nissan in the Note, replaced R134a with this new gas, generally called R1234YF. Unfortunately, as well as being flammable, it appears to be more prone to leaking from systems and when it does the high cost of the gas makes a re-gas much more expensive.

The EC Competition Commission urgently needs to look into this matter because it appears there are very few manufacturers of HFO 1234YF and the price (up to 5 times as much) has now made the price of R134a much more expensive.

More at the bottom of: www.airconditioningforcars.co.uk/ACpage06

And also at: www.ac4cars.co.uk/r1234yf.html 

For more information, link to www.autoair.co.uk

Air conditioning specialists include:

• Air conditioning parts: autoairconparts.co.uk

Airconconditioning For Cars (+ useful informarion) www.airconditioningforcars.co.uk

• Arctic Air UK, Milton Keynes http://arctic-air.co.uk/

• Aircon Direct of Gravesend www.ac4cars.co.uk Tel 01474 832941 Family run company. They have mobile units based in Northfleet Kent (Near the M25 Dartford crossing and Bluewater Shopping Centre). Cover Kent, a little of SE London and Surrey, Sussex or Essex when requested (highly recommended).

AVACS Limited Unit 2, Kerridge Industrial Estate, Station Road, Alton Hampshire GU34 2PT. Tel: 01420 80808. 

Autosolutions-Aircon (London) website: www.autosolutions-aircon.co.uk Sensible, straightforward FAQ answers, too. Tel: 02084221212.

Institute of Vehicle Air Conditioning www.instvac.co.uk (some information out of date

• Autoair Gary Soames of Autoair, independent Air Con Consultant comes to your car, Surrey area. Website www.autoairconditioningltd.co.uk

Automotive Cooling Services Agents and fitters of Diavia aftermarket air-conditioning systems, tel: 01604 639005, website: www.automotivecoolingservices.co.u

Air-Care-Automotive (Surrey and London) website: www.air-care-automotive.co.uk

Coolair UK Ltd (guarantees its work), head office: Kingsley Road, Lincolnfields, Lincoln LN6 3TA, tel: 01522 682288, and ask for Emma Hayward or Nikki Miller to put you onto your local branch.

David Norton, Kingsfold Garage, Dorking Road, Kingsfold, West Sussex RH12 3SB, tel: 01403 750202.

Readerair www.readerair.co.uk, tel: 01483 726300.

MotorClimate UK (Birmingham), tel: 0121 766 5006. Tel 0121-766-5006. E-mail Info@motorclimate.co.uk, Website www.motorclimate.co.uk

Alpinair, Alpinair, Hanger Lane Gyratory www.alpinair.co.uk, tel: 020 8991 0055. Free Phone: 0800 197 2120

Vehicle Air Conditioning Services. Service Centre: Unit 8, Wintersells Road, Byfleet, Weybridge, Surrey KT14 7LF; Parts: Unit A, 120 Oyster Lane, Byfleet, Surrey, tel: 01932 355825.

Vehvac Ltd, Fircroft Way, Edenbridge, Kent TN8 6AJ, tel: 01732 868080.

Halfords Garages (see local Yellow Pages for numbers).

Autoclimate Ltd (trade only), Unit 37, Atcham Business Park, Atcham, Shropshire SY4 4UG, Tel. 0345 5050900, Fax. 0345 5050901 website: www.autoclimate.com.

Robert Newton MI AgrE, 16, Ridgeway, Hurst Green, Etchingham, East Sussex TN19 7PJ, tel: 01580 860489/07973 659391

Express Repairs (Ozzies) 14-15 Severside Trading Estate, Sub-Meadow Road, Gloucester. Tel 01452 505599 Excellent air con repairs, refills from £52 inc vat.

ColdStart, on little Tennis Street in Nottingham (a recommendation from The Backroom).

Ariazone International Marcus Dixon at Ariazone International, Port Talbot Tel 01639 822111. info@ariazone.co.uk www.ariazone.co.uk

Reader Air Conditioning Boundary Business Centre, Woking, tel 01483 726300

Coolaircon www.coolcaraircon.co.uk Midlands based mobile service freefone 08700 669929. More than 9,500 a/c parts available online, mobile a/c re-charge, service and repair.

Car Aircon Services Ltd www.carairconservices.com, Beehive Road, Brampton, Chesterfield, Derbyshire S40 2RD, run by Geoff Parker, telephone 01246 238284 or mobile 07836 368336.

Auto Air Con Services Tel: 01983 554904. Mobile: 07778 528986.

Airconditioning Compressor Remanufacturing Service, saving customers ££££££ Hundreds on the Vehicle Mfg Retail Prices:

Compressortech (Birmingham) Tel 0121-766-5006
E-mail sales@compressoretech.co.uk Website www.compressortech.co.uk

Airconditioning Parts Supplier


Air-Conditioning and Fuel Economy

A lot of nonsensical generalisations have been written about this.

Basically a/c takes 5 - 10bhp from the engine.

So while it will affect the fuel economy of a car with 50bhp, the driver of a car with 500bhp won't notice it. And in fact, cruising at 70mph in a car with a relatively normal 110bhp, any increase in fuel consumed is insignificant. Opening the windows will have a far more detrimental effect because of the increased resistance the engine is forced to work against.

You will notice a more significant drop in economy in traffic because then the engine is idling and not moving the car very much for the time it is actually running, while at the same time it is turning the a/c pump. So in traffic or about town, at relatively low speeds, where opening the windows creates less aerodynamic drag, it will save more fuel to open the windows than to run the a/c.


Reconditioned a/c pumps (or your own pump reconditioned in 48 hours): www.compressortech.co.uk


Airconditioning condenser protective grilles: www.zunsport.com


Airconditioning conversion kit R12 to R134aAutoParts 2020 Cool Air Kit  (If your car has a/c using the old R12 CFC gas which is now illegal, you can buy a conversion kit to the legal R134a gas, recommended by a reader who did this years ago in a US import Honda Accord and has not had any trouble since. 


Smells from air-conditioning

Paul Evans of 


www.chillywillys.org writes: 

I noticed one or two concerns on your forums regarding nasty niffs created by a bacterial build up on the air conditioning evaporator. We have some experience of this and investigated alternative treatments extensively as the products we had used previously were ceasing to be effective. We conclude that this is for two reasons; Bacteria develops a resistance to certain products and access to the evaporator itself has become more difficult. In most German vehicles it is secured in a sealed box with the heater matrix and is not usually visible. Japanese vehicles have a separate evaporator thus encouraging airflow around it and discouraging bacterial growth in the first place. In the worst cases bacteria flow through the vents causes nausea, headaches and a runny nose. There is a product marketed by Wurth, this is rather like the old smoke machines that atomise a liquid product through the recirculation flap in the passenger footwell. We have used this for three years now with 100% success. The process takes about 45 minutes combined with an a/c service. The alternative options seem very hit and miss, bombs leave a residue and aerosols may or may not get it depending on where the bacteria is developing. We looked at about a dozen or so alternatives before taking this (the most expensive ) option. Wurth is so sure of its atomised sterilisation product it is supported with a 12 month guarantee.

Alternatively, get a can of Autoglym Air-Con Sanitizer (RRP £11.99) and follow the instructions. Requires leaving the car running with the vent switched to recirculate for 15 minutes while you stand outside and watch.








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