Volkswagen Polo Service & Repair Manual: Pressure Gauge, Tests and Measurements

Volkswagen Polo Service & Repair Manual / Refrrigerant R134a Servicing / Refrigerant Circuit General Information / Pressure Gauge, Tests and Measurements

Indicators on pressure gauge

1 -	Temperature scale for refrigerant R134a CF3–CH2F or CH2F–CF3.

2 -	Pressure scale

The pressure gauge may have one or more temperature scales next to the pressure scale. The R134a scale values are allocated respectively in the vapor pressure table. Since various refrigerants create different vapor pressures at the same temperature, each temperature scale is identified for the respective refrigerant.

Pressure Gauge Uses

a – Pressure and temperature measurement at refrigerant circuit

High pressure gauge measures pressure and temperature, which expand uniformly from outlet of A/C compressor via the condenser up to constriction (restrictor, or expansion valve) with A/C system switched on.

Low pressure gauge measures pressure and temperature, which expand uniformly from constriction (restrictor, or expansion valve) via evaporator up to input of A/C compressor with A/C system switched on.

Note

The relationship between pressure and temperature indicated on the gauges only exists in a refrigerant circuit that contains liquid or vapor, but not gas. In a gaseous state, the temperature is approximately 10 °C (50 °F) to 30 °C (86 °F) higher than indicated on the gauge.

b – Verification of refrigerant in a closed container

Refrigerant R134a is present in a closed vessel or in a refrigerant circuit when the temperature indicator on the gauge matches the refrigerant temperature (the temperature of standing fluid is equal to the outside temperature).

A closed vessel or a refrigerant circuit that has been switched off is empty when the temperature indicated on the gauge is below the temperature of the refrigerant.

Note

The relationship between pressure and temperature indicated on the gauges no longer applies if no liquid is present and the pressure is built up solely by gas.

Pressure Gauge, Tests and Measurements

Refrigerant Circuit with Restrictor and Reservoir

Arrows point in direction of refrigerant flow. A-Low pressure side of refrigerant circuit. B-High pressure side of refrigerant circuit. ...

A/C Service and Recycling Units

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Other materials:

Additional Information Sources
Technical Service Handbook outlining action to be taken to rectify current problems. For the repair manual for model-specific repair work. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87. ...

Towing a trailer
First read and observe the introductory information and safety warnings Headlight adjustment Towing a trailer can raise the front end of the vehicle enough for the dipped beam to blind other road users. Use the headlight range control to lower the light cone as required. If you do not have ...

Refrigerant Oil
Refrigerant oil mixes with the refrigerant (about 20 - 40%, depending on compressor type and amount of refrigerant) and circulates constantly in the system, lubricating the moving parts. Special synthetic refrigerant oils, for example, ...