This is purely a guide on what to look for and common issues on the GTi-6 aircon setup, and to break things down to give you an idea of what's what.

How aircon works
Aircon has 2 sides, a low pressure side and a high pressure side.

All current vehicle air-conditioning systems work on a loop system with refrigerant being recirculated around it. The compressor is belt driven from the engine and compresses the refrigerant to a high pressure in gas form.

It is then piped to the condenser situated in front or beside the radiator, where fan assisted air cools the gas which condenses to a warm liquid - still under high pressure.

Some systems use a receiver drier and expansion valve, in these types of system the liquid refrigerant passes through the receiver to remove moisture, impurities and to separate gas bubbles from the flow. It then passes to the expansion valve which restricts the flow creating a cooling effect in the evaporator as the liquid evaporates due to the reduction in pressure. The expansion valve closes at about 2°C to stop ice formation inside the heater box restricting the airflow as moisture collects from the rapidly cooled air. The gas is then returned to the compressor via the larger of the two pipes for another cycle.

On other systems the cooling effect is achieved by restricting the flow of liquid in the inlet pipe to the evaporator, the resultant drop in pressure giving the cooling as the liquid vapourises absorbing heat from its surroundings in the evaporator. The gas is then passed through an accumulator to prevent liquid refrigerant returning to the compressor and causing damage. This type of system is regulated by a pressure switch on the return line switching the compressor off if the pressure goes below a preset point.

Warm air can hold much more moisture than cold air so as the air is rapidly cooled moisture is released and collects in the bottom of the heater box. This drains out through a small pipe to exit under the vehicle. Because the heater box is often damp, mould growth can become a problem, causing bad smells.

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Aircon components

Compressor

Condenser

Evaporator

Filter/dryer/receiver

Pipes

Sensor

Pollen Filter

Gas

Compressor
Open the bonnet, you will see a big round thing that looks like an alternator which is also belt driven, it is located at the front driver's side at the very bottom of the car.

Condenser
This is like a small radiator which sits in front of the actual radiator.

Evaporator
This is located behind the dash, behind the glove box/airbag module.

Filter/dryer/receiver
This removes moisture and has a filter in it which remove inpurities and is located under the bonnet, on the driver's side, almost next to the filler cap for the windscreen washer fluid top up.

Pipes
There is an array of pipes, going from the drivers side across the front of the car under the radiator and then up into the passenger side of the car through the bulk head via a small black box which leads into the evaporator.

Sensor
The GTi-6 has climate control on Phase 2/3 cars. The sensor for this is located in the roof, near the map lights. You will see a small air vent type plastic cover, the sensor is behind this, which monitors cabin temperature.

Pollen Filter
This traps pollen and bacteria.

Gas
The gas used is a common refrigerant called R134a. This is more friendly gas which doesn't harm you, or the environment. Cars built pre 1992 had a different gas called RS24 which although is more efficient, is more dangerous. The 306 GTi-6 holds about 0.6kg of R134a gas.

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My 306 GTi 6 aircon turns on and off at random!!
Aircon will turn itself on automatically if:

1. The temperature is above 25°C (as indicated on the display) and you want cold air
2. If you want hot/cold air on the windscreen (if the windows are misted up - not sure how it detects this - humidity sensor presumably)
3. If you turn on the car and it's very hot in the cabin and you put it cold
4. If you had aircon on when you turned the engine off

It also turns off on the following conditions:

1. If you floor the cars throttle WOT (Wide Open Throttle), aircon turns off to give you more available power for safer overtaking
2. If you start the car and the temp is 3°C or below. However the humidifier still works which is why it'll clear frost and mist quicker in the winter. Note this isn't strictly using air conditioning as it will not engage at low temperatures.

Fault finding
Remember, just because your A/C button light comes on when you press the button doesn't necessarily mean your aircon is working.

If your aircon is working:

Light on the A/C button comes on

Revs fluctuate and then stabilise but near 1000rpm instead of 750rpm

You hear a click from under the bonnet

You get cold air

Your aircon doesn't work:

No gas

Leak in the system

Failed component

Outside temp is below 0°C

A system without gas has no pressure, so if the system is empty the compressor won't turn on. If the compressor doesn't turn on, you won't hear the click under the bonnet and your revs won't rise when you hit the A/C button.

First step from here is to call out an engineer/take the car to a garage and have the system re-gassed. 99% of places will first test the system for leaks, by filling the system with nitrogen to see if it holds pressure. If all is well then they will put oil and gas into it.

Typical pressures are
Low pressure side: 5 bar (approx)
High pressure side: at least 7 bar. In the summer this can rise to almost 30 bar (approx)

With the system re-gassed, when you hit the button the compressor pump should kick in then you will hear a click and should see your rev needle rise. If this doesn't happen, your compressor is faulty and needs replacing.

If your system doesn't hold the above pressures then there's a leak somewhere. At this point the person who you've taken it to should fill the system with a UV (ultra violet) dye. Because this is UV it isn't visible to the naked eye and requires either special UV glasses or a UV torch to spot. They will pressurise the system again with nitrogen and the dye and try to locate the leak. This should pin point where the leak is, and your air con engineer should give you an appropriate quote for a repair.

Note: By law an aircon engineer HAS to fully drain your aircon system before refilling because the system must be placed under a complete vacuum to recharge it, that's how the gas goes in.

At this point I should point out a few things. Leaks sometimes don't show up first time round. This is dependant on a few things:

1. Current environment temperature
2. Worn part

If you have your system tested and re-gassed on a really cold day, it may not show up leaks. This is because the gas doesn't expand very well when cold, so the aircon system isn't under any real strain. A leak may not be apparent on a cold day and may work fine until summer arrives and the gas expands.

A worn part like a condenser pump or evaporator may fail because of not being used. If the system starts being used after a while, the components/rubber seals may have seized up and failed.

What parts typically fail?

Compressor

Condenser

Evaporator

Pipes corrode

Seals degrade

What common parts on a 6 fail?
Mainly pipe work. Because of the pipes are located under the radiator, excess coolant leaks onto the pipes and causes them to corrode. Also splash back from salty/wet roads doesn't help. You can get protective sleeves made up for them, or just coat them in grease/vaseline to help preserve them.

Even the newest GTi-6 will be almost 6 years old now. It's typical that a pipe or rubber seal will fail. Most 3rd party aircon specialists will replace these and be cheaper than Peugeot.

Worst case scenario?
The worst case scenario of a failed aircon system on a GTi-6 is the evaporator or a leak behind the dash, the reason being that you have to remove the entire dashboard to access it, reseat airbags and a whole host of other things. Peugeot quote 12 hours in their technicians manual to remove a 306 dash. As you can imagine this becomes quite pricey and bills can run up to £1000 if done by a third party. It'll be much more at Peugeot.

Other bits of info

The typical temperature of air output if aircon is working is about 5°C.

Typically aircon will be most functional and fully effective after 10 mins of driving.

The hotter the ambient temperature of your environment, the more the gas in the system expands, the more it expands the colder it gets. This is why an aircon system will work for say 4 months after a re-gas, but in the height of summer it will leak due to the increase in pressure and a fatigued system.

Aircon needs to be used at least 10 mins per week. Within the gas is an oil based lubricant which keeps the inside of your aircon system in tip top shape, if they aren't lubricated they break down and fail. Running aircon for at least 10 mins ensures the system is lubricated enough to remain functional.

All aircon systems that are in perfect condition will leak, this is normal. You don't notice it as the leak is so small. Typically a car that runs aircon all the time will eventually run out of gas, this will take around 3 years, however in some cases it can be up to 6 years before it completely empties. This is normal.

Has my car got a water leak?
Well possibly! However if in really hot weather you notice a patch of water near the front passenger wheel after you've been out driving and used aircon, don't worry. This is the system taking the moisture out of the air (which helps it cool quicker) and dumps it on the road.

What can aircon do?

Cool you down in the summer

De-mist all your windows rapidly in the rain

De-ice your windows in the winter

Most people think aircon is only for summer, they are wrong. Aircon is a tool that can be used all year round. In most modern cars if you turn your heater panel at the windscreen aircon turns on automatically and you cannot turn it off.

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