BMW 318/325/M3/525/535/M5 1989-1993 Repair Information

Air Conditioning Systems



R-12 and other chlorofluorocarbon refrigerants, when released into the atmosphere, may contribute to the depletion of the ozone layer of the upper atmosphere. Ozone filters out damaging ultraviolet radiation from the sun.

Consult the laws in your area before attempting service on the air conditioning system in your vehicle. In some states it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician.

The air conditioner is filled with refrigerant R-12 or R-134a, which produces very high pressure even when the system is not operating. Not only can a component broken by mishandling, crack or break explosively, but the escaping refrigerant will immediately drop to -27°F (-33°C), causing severe frostbite to any part of the body exposed nearby. The problem is worsened by the fact that refrigerant systems employ thin sections of light alloys to transfer heat efficiently-thus, components are readily damaged by inexperienced mechanics.

Thus, we recommend that you make no attempt whatever to repair any component on the air conditioning system. If a refrigerant component must be moved to gain access to another part, we recommend you leave at least the part of the job involving the refrigerant component to someone with the specialized training, tools, and experience to handle the job safely. However, if you are going to work on the system yourself, you must be very careful and use common sense before making any repairs.


Once a year, before hot weather sets in, it is advisable to check the refrigerant charge in the air conditioner system. This may be accomplished on R-12 filled systems by looking at the sight glass located in the engine compartment. First, wipe the sight glass clean with a cloth wrapped around the eraser end of a pencil. Have a friend operate the air conditioner controls while you look at the sight glass. Have your friend set the dash panel control to MAX cooling. Start the engine and idle at 1500 rpm. While looking at the sight glass, signal your friend to turn the blower switch to the HIGH position. If a few bubbles appear immediately after the blower is turned on and then disappear, the system is sufficiently charged with refrigerant. If, on the other hand, there are a large amount of bubbles after the blower has operated for a few seconds, then the system is in need of additional refrigerant. If no bubbles appear at all, then there is either sufficient refrigerant in the system, or it is bone dry. The way to clear this question up is to have your friend turn the unit OFF and ON (engine running at 1500 rpm) about every 10 seconds or so while you look at the sight glass. This will cycle the magnetic clutch. If the system is properly charged, bubbles will appear in the sight glass a few seconds after the unit is turned off and disappear when it is turned on although they may linger awhile in extremely hot weather. If no bubbles appear when the unit is in the OFF position, then the system should be serviced by an authorized dealer and checked for leaks. Do not operate the unit if you suspect that the refrigerant has leaked out.

Check the radiator and condenser for clogging by bugs and road debris. If the fins of the radiator and condenser are blocked, heat cannot be transferred from the fins to the airstream. Clean the debris from the fins to restore the airflow.


BMW recommends the use of their special charging and recovery system for both R-12 and R-134a systems. The unit is manufactured by BEHR and is designed for use by a trained technician. If your vehicle requires the air conditioning system to be discharged and later charged, let a trained and certified technician perform the work.