Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Components, Replacing: Notes
There is a risk of freezing.
Refrigerant may leak out if the refrigerant circuit is not discharged.
Refrigerant must be extracted before opening the refrigerant circuit. If the refrigerant circuit is not opened within 10 minutes of extraction, pressure may form in refrigerant circuit due to evaporation. Extract the refrigerant again.
- All components of the refrigerant circuit submitted for quality observation are always to be sealed (use original sealing caps of replacement part).
- To date, the following replacement parts (A/C compressor, reservoir, receiver/dryer, evaporator and condenser) have been filled with nitrogen gas. This charging stops gradually or the charging pressure is so low that gas does not escape noticeably when opening.
- On vehicles installed with a compressor with no A/C clutch, the engine is only to be started following complete assembly of the refrigerant circuit (A/C compressor always in operation as well).
- When the refrigerant circuit is empty, the A/C compressor with A/C Compressor Regulator Valve -N280- (without A/C clutch) is switched to internal lubrication with the result that only a minimal amount of oil is pumped from the A/C compressor into the circuit.
As parts are sometimes stored for lengthy periods and at different locations within the spare parts organization, it is entirely possible that gas will escape from some parts and not from others on initial opening (even in the case of identical spare part numbers). Sealing caps at replacement part connections are therefore to be removed carefully and the nitrogen gas allowed to escape slowly.
The refrigerant circuit is equipped either with a restrictor and a reservoir, or with an expansion valve and receiver/dryer.
The dryer cartridge or components with desiccant bag (reservoir, receiver/dryer) are always to be replaced after cleaning the refrigerant circuit by flushing with refrigerant R134a (refer to Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING) WITH REFRIGERANT R134A ), or blowing through using compressed air and nitrogen (refer to Refer to REFRIGERANT CIRCUIT, CLEANING WITH COMPRESSED AIR AND NITROGEN ) in doing so, leave sealed as long as possible to minimize absorption of moisture.
Replace the dryer cartridge or the components with a desiccant bag (reservoir, receiver/dryer) if it is required for certain repair procedures or if the refrigerant circuit has been open for a longer period of time and moisture has gotten in (after an accident, for example). Refer to Refer to LEAKING OR DAMAGED COMPONENTS EXCEPT A/C COMPRESSOR, RESERVOIR OR RECEIVER/DRYER .
The period of time which a refrigerant circuit may be left open without having to replace a component with the desiccant bag (reservoir, receiver/dryer) depends on ambient influences to a large extent. Given a high ambient temperature and a high humidity level or if the vehicle, for example, has been standing in the open or driven (in wet, foggy weather conditions), the period will be considerably shorter than for a vehicle which has been standing in a heated dry area. The size of the opening through which moisture may ingress into the circuit also influences the period for which a refrigerant circuit can be left open without having to replace the component with the desiccant bag. Refer to Refer to LEAKING OR DAMAGED COMPONENTS EXCEPT A/C COMPRESSOR, RESERVOIR OR RECEIVER/DRYER .
Seal open connections and pipes (to prevent absorption of moisture).
Always replace the restrictor.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.