Car Air Conditioning Problems
*Always insist that you see the repair shop's "F" gas certificate.*
This is the very basic requirement for anyone handling your car a/c.
A/C failures or lack of cooling can be categorised as follows:
1- No Gas
Air conditioning system is equipped with pressure switch (sensor) which cuts off power to the compressor to protect the unit from running dry and seizing up.
Every car requires recharging with refrigerant at least once every 2 years and it does not necessarily means that there is a leak in the system, the low refrigerant in the system contributes to low cooling or triggering the pressure switch to shut down the system, nevertheless recharging the system can get the a/c working but a through inspection of the system must be carried out at this stage.
Systems are prone to leakage under specific circumstances such as leaving the a/c switched off for long periods of time specially during the winter times, corrosion in the aluminium pipes and condenser, the 134a gas is corrosive to aluminium and condensers are manufactured from alloy of this metal, ideally the internal tubing of the condenser should be coated with zinc to protect the condenser against adverse effects of this gas, but since the process is expensive then the manufacturer’s disregard this important factor in construction of the condensers and need for replacement becomes necessary, unfortunately the problem is persistent and regular and in most cases the owner of the vehicle can see the problem through visual inspection. This inspection shows oily shadow in some parts of the condenser and therefore, recharging should be avoided until the problem is addressed, this is an important factor that is disregarded by many garages who claim to do recharging of the a/c systems alongside other jobs, one must bear in mind that the oil in the compressor is mixed with refrigerant which circulate through the system and at every leaking point, part of this oil is discharged along with refrigerant leaving the compressor to run low on oil, it is this oil that causes the shadow on the condenser and should be replaced every time that a leaking car requires to be recharged even with the knowledge of the owner who is not prepared to foot the bill for repairs, unfortunately, gradually the compressor will seize creating much greater cost. The customer must insist that following a visual inspection, dye is injected into the system for future inspection with ultra violet light, and an electronic leak check is carried out before the vehicle is released.
3- Component Failure
This comprises of Compressor, pressure switch , Expansion Valve & Auxiliary fan.
Compressor failures are mostly attributed to lack of proper a/c servicing and lack of correct Leak management as described above, in this case compressor will not create pressure and suction despite running, or is seized totally. In such circumstances technicians should replace the Expansion valve, Receiver/Dryer and flush the system before fitting a new compressor, this procedure ensures that all metal particles in the system from the old compressor along with contaminated oil is removed ensuring compressor’s long life and protection of your investment, in many cases most garages simply replace the compressor for a quick profit leaving the new compressor at the mercy of time before it seizes again.
The pressure switch failure results in the unit not sending a signal to the control panel to activate the a/c system, the part is inexpensive and in most cases easy to replace, unfortunately many garages regard this as compressor failure and without proper equipment and knowledge put the customer into unnecessary expenses.
Expansion valve failure contributes to lack of improper working of the system with little or no cold air at the vents, the process is simple and inexpensive, but requires knowledge of gauge reading prior to dismantling and replacing the part.
Auxiliary Fan is an important part of the system, in some cars vehicles are fitted with extra fan in front of the condenser to lower the pressures in the system or are fitted with one single fan with dual purpose of cooling the water radiator and the a/c condenser, the lack of operation of this fan due to wiring problem/Relay/seizure or pressure switch not working gives rise to continuous high pressures in the system, which will affect the cabin temperature or result in compressor failure. To check for this and proper functioning of pressure switch you need to start with an empty system, once the a/c switch is pressed the compressor must not work, this means that pressure switch side of the low refrigerant protection is working, by adding gas the compressor cuts in ensuring the same again, after fully charging the system the high side hose from the compressor starts to warm up, to a pint that it can not be touched due to rise in the temperature, at this point the Auxiliary fan cuts in and lowers the temperatures to within safe working pressures, therefore ensuring that the high side part of the pressure switch is also working and therefore, ticking all the boxes in the favour of the pressure switch. If touch method or high gauge reading fails to see the fan activating, then pressure switch and fan needs to be examined, by direct feed from battery to the fan, the fan should work, if this happens then the pressure switch is faulty, otherwise the fan is seized and requires replacement, under this circumstances, and until repairs are carried out the customer must refrain from switching on the a/c system unless he is driving on the road without interruption, since the ram air entering the condenser acts as a fan. In some cases as soon as the a/c system is switched on the auxiliary fan is activated and runs on low speed, this speed increases according to the outside temperature and duration of the time that the a/c is left switched on, this is an ideal design since the pressures in the system is kept low at all times providing longer life expectancy from the a/c components.
Electrical & Electronic component failure.
As times passes more and more cars are fitted with sophisticated electronic control panels giving rise to problematic functioning of the a/c system, in most cases there are no relays present in the system and all work is carried out through one single control panel, nevertheless, any fault in this unit is not repairable and whole unit must be changed at great expense but the parts associated with this unit are more commonly at fault and not the control panel itself, some of these components can be listed as interior and exterior temperature sensors, fault within these parts are only traceable using electronic fault diagnostic machines, and must not be guessed if the garage lacks the proper equipment.
Over Charging Problems
In many cases we have received vehicles from other garages who have charged the systems but could not understand why the system failed to cool, they complained that the compressor keeps clicking on and off, and had diagnosed the problem as Compressor failure, where the problem was initially created by themselves. On one occasion we recovered 1500 grams of gas from a vehicle where it should have been charged to 650 grams, this caused extreme pressures in the system and auxiliary fan could not cope with such high pressures and therefore, the pressure switch switched off the compressor to protect it, the short period that compressor was off, the system pressures had the chance drop sufficiently to switch the compressor back on again, and the cycle continued. If at this stage the gas was not brought back to the recommended level, then the compressor would have seized in time as a result of overcharging. Ensure that once your vehicle is charged and before leaving the garage, all above points are carried out and system is functioning to your satisfaction.
Air Conditioning Smell
In many occasions customers complain about smell inside the cabin, and ways to remove it. Currently there are products on the market such as chemical tins being placed inside the car to remove the smell, unfortunately these are glorified "Air Fresheners" that not only they do not address the problem instead they make a bad situation worse, one needs to look at the root of the problem before engaging in spending money on these products. The problem lies inside the heater box situated behind the dashboard, this part of vehicle houses the heater matrix (radiator), air conditioning matrix, flaps and other related items providing services such as heating, cooling and mixing of hot and cold, the environment inside this box is humid due to presence of heat, cold and condensation water generated from the a/c matrix, this environment like a tropical jungle provides the perfect place for pollen and other impurities entering it from outside atmosphere to grow and cause foul smell inside the vehicle, not only the smell is unpleasant it is also unhealthy to breath specially for those who suffer from asthmatic conditions. The pollen filter in the cabin provides some protection but still lets through some impurities specially when the a/c is on re-circulation mood and the windows are lowered down. Fortunately chemicals to address this problem are available but they need to be injected into the heater box to wash and clean the interior of the heater box. This procedure requires experience and care to achieve the perfect results, but at the same time, a change of pollen filter on regular intervals will help the situation. Next time that your carbon filter is changed, ask your mechanic to save it for you, by examining the contents inside the pollen filter you will realise the variety of impurities in the atmosphere that enters your cabin......