Volkswagen Golf Service & Repair Manual: Checking pressures

Volkswagen Golf Service & Repair Manual / Air conditioning system with refrigerant R134a / Checking pressures on vehicles / Checking pressures in refrigerant circuit (using air conditioner service station) / Checking pressures

Switch off ignition.

–	Connecting air conditioner service station → Chapter.

–	Read pressure from pressure gauges; two results may be displayed.

Ambient temperature (in degrees centigrade)	Pressure in the refrigerant circuit in bar positive pressure
+15°C	3.9
+20°C	4.7
+25°C	5.6
+30°C	6.7
+35°C	7.8
+40°C	9.1
+45°C	10.5

Note

The temperature of the components of the refrigerant circuit should be the same as the ambient temperature.

If individual components of the refrigerant circuit are warmer or colder, then the pressure will deviate from the values shown in the tables.

Absolute pressure means that 0 bar corresponds to an absolute vacuum. The normal ambient pressure (positive pressure) corresponds to 1 bar absolute pressure. On most pressure gauges, a reading of 0 bar corresponds to an absolute pressure of one bar (which is confirmed by the existence of - 1 bar marking beneath the 0 scale marking).

Where vehicles have a high-pressure sender -G65- which indicates the measured pressure in the measured values block, the measured pressure should agree with the values in the tables.

→ Rep. gr.87

The pressure in the refrigerant circuit is lower than indicated in the table

Insufficient refrigerant in circuit.

–	Check for leaks in the refrigerant circuit → Chapter.

–	Check the high-pressure safety valve.

If the high-pressure safety valve has blown off:

–	Check activation of radiator fan.

–	Check refrigerant pipes and refrigerant hoses for restrictions in cross-section at bends that have too tight radius.

–	Check refrigerant pipes and refrigerant hoses for external damage.

–	If no defects are found, blow through refrigerant circuit with compressed air and nitrogen.

The pressure in the refrigerant circuit is equal to or greater than that in the table

–	Start engine.

–	On vehicles with electrical air conditioner compressor, switch off ignition.

WARNING

High voltage on high-voltage system of hybrid vehicle. Danger of electric shock! Before starting work, carry out a visual check of high-voltage components in area of work. Comply with general warnings → Hybrid electrical system; Rep. gr.93.

–	Set air conditioning system for maximum cooling output.

Note

If the low-pressure switch had been removed in order to connect the air conditioner service station, bridge the electrical connections in the respective connector for pressure measurement.

The air conditioner compressor is driven by the engine via the air conditioning system magnetic clutch -N25-.

The air conditioner compressor regulating valve -N280- is activated by the Climatronic control unit -J255-.

→ Rep. gr.87

If the air conditioner compressor is not driven or the regulating valve not activated when the engine is running:

–	Determine the cause, e.g. by reading the event memory for the air conditioning system, and rectify it.

–	Observe the test prerequisites.

–	Check power supply for air conditioning system magnetic clutch -N25-. If this is OK, repair magnetic clutch.

–	Check actuation of air conditioner compressor regulating valve -N280-.

→ Rep. gr.87.

Test prerequisites

Radiator and condenser must be clean (clean them if necessary). The heat insulation on expansion valve is OK and properly installed. See ...

Continuation of checking pressures

Where vehicles have a restrictor and reservoir, check these (with internally regulated air conditioning system compressor) → Chapter. ...

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