When you cool a substance it means that you remove the heat from it. For the type of air coolers used in air conditioners you usually use the principle that if a fluid passes from high pressure to low pressure, that fluid will absorbs heat from its surrounding.
Refrigerant:
Until the beginning of the year 1990 R12 were used as a refrigerant, today R12 is forbidden from being used and were replaced with R134A. You can convert a R12 system into a R134A system, but it is important to remember that R12 is using a mineral based oil while R134A does not mix with mineral oil, instead you need a ester/synthetic oil for your compressor type as well as the R134A refrigerant. The old mineral oil can still be left in the system but new oil of the right type needs to be filled into the system. The oil in a A/C system is transported around the whole system by the refrigerant and lubricates the compressor. You should also install new service nipples with quick connect fittings and refill with a smaller amount of refrigerant. The system shall also be marked clearly stating the refilled amount of refrigerant as well as the conversion to R134A..
Both R12 and R134A systems can be converted into R600A/R290, which is included in SPEEDPARTS refill kit, this refrigerant mixes well with both mineral and ester/synthetic oil. In other words, you do not need to exchange the oil but you need to mark the system clearly that it has been converted as well as the amount that has been refilled..
Filling quantities for R600A/R290
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900 94-98 filling quantity 268g
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900 sankyo 81-93 filling quantity 336g
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900 Clarion 81-93 filling quantity 388g
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9000 85-89 filling quantity 407g
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9000 90-98 filling quantity 336g
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9-3 98-02 filling quantity 296g
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9-3 03-12 filling quantity 251g
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9-5 98-01 filling quantity 324g
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9-5 02-10 filling quantity 305g
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9-5 10-12 filling quantity 222g
AC: The different parts
Evaporator
The conversion from high pressure to low pressure is conducted in the evaporator, it is this conversion that removes the heat from interior of the car. The refrigerant is guided into the evaporator as a fluid and is there transformed into a gas.
Expansion valve
The expansion valve regulates the flow rate in the A/C system so to reach the correct vaporization temperature in the evaporator.
Compressor
The refrigerant gas is sucked into the compressor as well as the evaporator ( this side is called the suckside/low pressure side which has thicker pipes and are cold). The compressor then compresses the gas into a high pressure again ( this sida calls the high pressure side which has thinner pipes and is warm).
Condenser
The gas is guided to the condenser for condensation, which means that this is the point where the gas is transformed back into fluid. The fluid is then guided back into the expansion valve/ evaporator again.
Condenser ventilator
The condenser ventilators purpose is to cool the condenser, so that the A/C performs within the correct pressure range with the aim to reach the optimal condensing, without exceeding the systems max pressure.
Dry filter
The dry filters purpose is to absorb moisture from the system. During a replacement of the compressor you should always replace the dry filter as well. If the system have been open for a longer period the filter should be replaced during a refill.
Pressure switch
The pressure switch tells the system when the compressor shall start and stop depending on the momentarily pressure in your A/C system. Usually the pressure switch is of a multipurpose type, in this cases it also have the purpose to control the condenser ventilator.
Service
As long as it works, a A/C system does not require any service. If the gas leaks out of the system, troubleshooting will be required and any leaks needs to be fixed before any refill is made. To be allowed to refill, or any other handling of R134A, there is a specific certification and education required. SPEEDPARTS refill kit and the refrigerant, R600A/R290, does not require any certification and neither any education since it is completely eco-friendly.
Advices for Troubleshooting
The A/C compressor turns itself on and of in short cycles that lasts for a few seconds
Likely cause of error:
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Shortage of refrigerant
Measures: Empty the system and fill it with the right amount of refrigerant
The compressor runs for a longer period of time but there is no cooling
Feel the thicker and the thinner pipe. The thinner pipe should be warm ( around 50 degree celsius) and the thicker pipe should be cold ( below 0 degrees celsius ). If both pipes have the same temperature and the compressor is running almost all the time…
Cause of error:
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The expansion valve is not able to regulate the pressure and needs to be exchanged
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The compressor have internal faults and needs to be changed
In both cases the dry filter should be exchanged as well so to prevent the problem from returning.
The compressor does not start even if there is refrigerant in the system
Cause of error:
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The fuse to the compressors magnetic clutch is broken ( Exchange if needed )
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The pressure switch is broken and does not enclose the electrical circuit to the compressor. You can control this error by checking the electrical schematic and connect the pins for the pressure switch connected to the compressor for a short period of time to see if the compressor starts.
Measures: Change the pressure switch, a lot of systems does not include a schrader valve which would allow you to change the pressure switch without emptying the system first and then refill it after the exchange.
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The compresors magnetic valve is faulty and needs to be exchanged.
Measures: Exchange the clutch alternatively exchange the whole compressor.
A/C is cooling on and of
Cause of error:
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he condenser ventilator is not functioning properly. Control the fuses, cabling and check if the fan is working by forcing it to run. Change if needed.
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The fan is working when forced to run but not otherwise. A lot of cars have a pressure switch with multifunctionality and in this cases the fan it controlled by the pressure switch, check the electrical schematics and force-feed at the pressure switch, if the fan starts the pressure switch needs to be exchanged.
Leakage
In older systems, that is not used during winter, it is usual for the compressors axial sealings to dry up a bit and will then let refrigerant out. This leakages can be troublesome to find since they plug themself once the compressor is running and refrigerant as well as oil if being pumped around the system. To prevent this it is recommended to run the A/C from time to time during the winter as well, you do know that the A/C is very good at removing moisture from your car interior? Other usual causes for leakages is the condenser as well as the pipes leading in and out from the compressor since these are placed in an exposed position. Remember that you always should change the O-ring on all of the places you loosen things on, always. The refrigerant that SPEEDPARTS sells is containing tracking liquid, which makes it easier to find possible leakages using a UV-lamp and by filling the system with a small amount of refrigerant.
Oil
Normally you never change the oil in a A/C system, with the exception that you are changing the compressor or something similar, neither is there an easy way to control the amount of oil left in the system more than a few test sticks that you can fizzle some gas on from the service valve. A lot of compressors comes pre-filled with oil and in these cases you should not fill any oils during an exchange. This is usually stated in the accompanying documentation that comes with the compressor, if this is not the case you have to check with the retailer. You should never fill a system exceeding its oil limit.
Refilling refrigerant
Refilling is done on the low pressure side, the thicker pipes. Look for the service nipple that is placed on the pipe/hose somewhere between the compressor and the evaporator. Before refilling a system with R134A you always have to perform a vacuum suction of the system, if you use R600A/R290 however this is not needed. If the system has been open for a longer period of time you do have to use desiccant first. Do not under any circumstances fill a system above its limits!