How to recharge Air Conditioning system

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Ray
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Currently Drives:: 2005 Megane Privilege - Now Sold
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How to recharge Air Conditioning system

Postby Ray » Sun Dec 30, 2007 6:31 pm

The Megane II/Scenic II/Laguna II all have 1 high pressure port. There is NO low pressure port available.

By using the correct equipment that is designed to use only 1 port and that..

1: Vacumns the system and checks for leaks
2: Weighs the refrigerant that has been removed.
3: Allows to you see the quantity of "PAG" oil that has been removed, so that you can add the same back.
4: Refills with the correct amount of refrigerant.

My advice is leave it to a "professional" - not neccesarily a renault garage!
Especially as it is highly illegal to vent R134a to the atmosphere.
So you buy a home recharge kit - You plug it in and "fill" the system. However you have a leak, where does the gas go? to the atmosphere!

So you have wasted the cost of the kit. You then have to get a professional to test the system using UV dye to find the leak anyway..

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Ray
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Posts: 3845
Joined: Mon Mar 21, 2005 1:11 am
Currently Drives:: 2005 Megane Privilege - Now Sold
Location: Hong Kong

Re: How to recharge Air Conditioning system

Postby Ray » Sat Dec 13, 2008 5:20 pm

andy_cc wrote:Hi Ray, Can i just correct some of the points above. As i am a refrigeration engineer by trade.

Most cars have two points of access to system, LOW side (suction, always the largest pipe on the A/C system) Normally visable in the engine bay, and the HIGH side (discharge, always the smaller pipe on the A/C system) this point of access isnt always visable, but is normall located close to the condenser, or on the pipe that come from the BOTTOM of the condenser.

You charge a system through the LOW side only (It is the LOW SIDE valve that is visable on the megane) as this works at low pressure approx 40-50 psi when charged. When the system is charging the low side SUCKS the refrigerant into the system as this is the suction side of the system. The low side of the system basically runs from the compressor to the evaporator behind the dash which is part of the heater matrix etc....

The HIGE SIDE access valve is only really used to check the operating pressures on this side on the system, this side of the system can run at anything between 200-300 psi all dependant on outside temps and temp of air being drawn over the condenser which is located at the front of the car in front of the radiator. Liquid refrigerant is present on this side of the system, The high side of the system runs from the evaporator to the condenser and back to the compressor, 134a refrigerants BOILING POINT is approx -30oC, so not only will it freeze the part of the body that comes into contact with it, it will also burn you at the same time, plus its under very high pressure! ive seen someone get hit in the face with high pressure liquid refrigerant, all i can say is, he is lucky he had glasses on otherwise he would be blind, but he was scared for life on his cheeks and nose!! SO NEVER TRY TO OPEN UP A REFRIGERATION SYSTEM WHEN IT IS RUNNING. In fact you should never atempt to open the system at all if you are not qualified

These recharge kits that you buy from halfords, are only really offered as a "TOP UP" and not a full charge. most cars have a charge of approx 600 grams of 134a. OK its not illgal to buy them (but it should be, as im not allowed to purchace refrigerant from my suppilers unless i have the right qualifications and premisie codes etc..) BUT IT IS ILLGAL FOR YOU TO ACCUALLY TRY AND USE THE KIT ON YOUR CAR, AS YOU DONT HOLD THE CORRECT REFRIGERANT HANDLING QUALIFICATIONS. (venting refrigeratant to the atmosphere carrys an unlitmited fine and/or imprissonment if caught)

If your car has no refrigerant init, theres a leak! this has to be investigated by carrying out a leak test on the system, 9 times out of 10 its one of two things.
1. stone has hit and split the condenser in which case the condenser will need to be replaced.
2. At every joint on the system theres a rubber "O" seal, if the unit hasnt been used for a while (ie. over winter) these seals can dry out and crack, (the refrigerant pulls a small amounts of oil through the system, this keep the seals lubricated), causing the refrigerant to weep out of the system, as it states in every user manual the system should be run once a week to stop the above happening! EVEN IN WINTER, HAVE THE HEATER DIAL SET TO AS WARM AS YOU LIKE AND JUST POP THE A/C ON, THE A/C WILL ACT AS A DEHUMIDIFIER AND REMOVE MOISTURE FROM THE CARS WINDOWS ETC.....
Charging a system for use that has a leak and has not been repaired also carrys an unlimitied fine and.or imprissionment if caught!

If you have a problem with you A/C, take it to the dealer, and if you dont want to use the dealer, find someone that speacailizes in Car A/C.
Dont take it to Kwik fit or Halfords, as these guys are just tyre fitters etc... at the end of the day they will just stick refrigerant into the system and "TOP IT UP". The amount of cars ive had to sort out after customers thought if was a cheep fix taking it to kwik fit etc rather than the dealers has risen. Most of the problems have been them over charging the systems with refrigerant, and most times its just a case of me degassing the unit, finding any leaks or faults etc... repairing and recharging. but ive had times when the system has been overcharged and its accually flooded the system with oil or blown the compressor which can be a very costly job to then put right.

HOPE THIS HELPS PEOPLE, IVE TRYED TO EXPLAIN IT IN SIMPLEST TERM POSSIBLE.
Andy


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