Get Air conditioning system -> 2.1 Working with air conditioner service station Guide for Volkswagen Touran 4 Door Second Generation (2015-2022)

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ Replacement compressors contain a certain specified quantity

of refrigerant oil. On vehicles with two evaporators, a certain

amount of refrigerant oil may also have to be filled in the circuit

if necessary ⇒ Heating, air conditioning; Rep. gr. 00 ; Tech‐

nical data and ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit; System overview - refrigerant circuit .

♦ If the air conditioner compressor does not need to be renewed,

replenish the refrigerant oil accordingly up to the prescribed fill

level (empty refrigerant oil and pour the prescribed volume

back into the air conditioner compressor or refrigerant circuit)

⇒ page 79 , ⇒ Heating, air conditioning; Rep. gr. 00 ; Tech‐

nical data; refrigerant oil .

– Completely reassemble the refrigerant circuit again ⇒ Heat‐

ing, air conditioning; Rep. gr. 87 ; Refrigerant circuit; System

overview - refrigerant circuit (vehicle-specific workshop man‐

ual).

– Evacuate and charge the refrigerant circuit in the prescribed

manner ⇒ “2.5 Evacuating refrigerant circuit”, page 140 and

⇒ “2.6 Charging refrigerant circuit”, page 146

– Bring the air conditioning system into operation in the prescri‐

bed manner ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit; Bringing air conditioning system into operation

after charging refrigerant circuit and

⇒ “2.7 Bringing air conditioning system into service after

charging”, page 149

1. Refrigerant circuit

125

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.7

Checking pressures with pressure

gauge

⇒ “1.7.1 Display on pressure gauges”, page 126

⇒ “1.7.2 Pressure gauges enable the following test and meas‐

urement work”, page 126

1.7.1

Display on pressure gauges

1 - Temperature scale for R1234yf refrigerant (CF CF = CH )

in °C

2 - Pressure scale in bar overpressure

Note

♦ Pressure is indicated in various units: 1 MPa (Mega-Pascal)

is equal to 10 bar or 145 psi; 1 bar absolute pressure is equal

to 0 bar, which is about the same as ambient pressure (at‐

mospheric pressure).

♦ This diagram shows a pressure gauge displaying pressure on

the low pressure side. The display here is shown in bar over‐

pressure (noticeable by “-1” in the display).

In addition to the pressure scale, the pressure gauges can have

one or more temperature scales. The scale values for R1234yf

are assigned according to the vapour pressure table. Because

different refrigerants have different vapour pressures at the same

temperature, each temperature scale is labelled for the respective

refrigerant.

♦ Pressure gauges enable the following testing and measuring

measures

⇒ “1.7.2 Pressure gauges enable the following test and meas‐

urement work”, page 126 .

1.7.2

Pressure gauges enable the following

test and measurement work

Pressure and temperature measurement in refrigerant circuit

♦ The high pressure gauge allows the pressure (and tempera‐

ture) to be measured with the air conditioning system switched

on irrespective of whether this is at the outlet of the air condi‐

tioner compressor through the condenser up to the restriction

(restrictor or expansion valve).

♦ The low pressure gauge facilitates measurement of the pres‐

sure (and temperature) that spreads evenly from the restric‐

tion (restrictor or expansion valve) through the evaporator up

to the inlet of the air conditioner compressor with the air con‐

ditioning system switched on.

Note

The relationship between pressure and temperature shown on

the pressure gauges is valid only where the refrigerant in the cir‐

cuit is liquid or vapour, but not when it is gas. In the gaseous state,

the temperature is approx. 10°C to 30°C higher than indicated on

the pressure gauge.

Evidence of refrigerant in a closed container

R1234yf refrigerant is present in a closed container or refrigerant

circuit if the temperature indicated on the pressure gauge corre‐

126

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

sponds to the temperature of the refrigerant (the temperature of

a standing fluid stabilises at ambient temperature).

A closed container or isolated refrigerant circuit is empty if the

temperature indicated on the pressure gauge is below the tem‐

perature of the refrigerant.

Note

♦ The dependency between pressure and temperature descri‐

bed on the pressure gauges no longer applies when there is

no liquid and the pressure is created by gas alone.

♦ Since the R1234yf and R134a refrigerant pressures are very

close to each other over a broad temperature range, it is not

possible to distinguish between them by means of the pres‐

sure measurement. It is possible to distinguish between them

e.g. by means of a gas analysis

⇒ “6.2.16 Analysis of refrigerant R1234yf”, page 24 .

1. Refrigerant circuit

127

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Air conditioning system -> 2.1 Working with air conditioner service station for Your Volkswagen Touran 4 Door Second Generation (2015-2022)

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