Get Refrigerant circuit -> 1.4 Investigating leaks Guide for Volkswagen Scirocco SUV Third Generation (2008-2017)

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

1.4

Investigating leaks

⇒ “1.4.1 General information about investigating leaks in the re‐

frigerant circuit”, page 68

⇒ “1.4.2 Searching for leaks in refrigerant circuits using an elec‐

tronic leak detector”, page 69

⇒ “1.4.3 Searching for leaks with UV leak detection system”, page

71

⇒ “1.4.4 Detecting leaks in a vacuum test using air conditioner

service station , or in a pressure test”, page 77

⇒ “1.4.5 Detecting leaks in a pressure test (with nitrogen or com‐

pressed air)”, page 77

1.4.1

General information about investigating

leaks in the refrigerant circuit

Note

♦ Small leaks can be detected with e.g. an electronic leak de‐

tector or a UV leak detector lamp.

♦ This workshop manual describes 2 ways of tracing leaks in

refrigerant circuits. These procedures have been tested and

lead to a reliable result under the different usage conditions if

they are performed correctly and in accordance with the spe‐

cific complaint.

♦ Various methods are offered in the open market with which

leaks in refrigerant circuits can be traced. These methods are

not able to provide clear results in all cases and, unless the

exact procedure is adhered to, they can also result in various

components of the refrigerant circuit being identified as having

leaks even though they do not. Furthermore, certain process‐

es can cause preliminary or permanent damage to the com‐

ponents of the refrigerant circuit

♦ Components that are found to be leaking must not be repaired.

They must be renewed instead.

♦ A leaking refrigerant circuit must not be charged with refriger‐

ant. Therefore, evacuate an empty refrigerant circuit and

check for leaks before charging the system with refrigerant

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

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Note

♦ VW/Volkswagen/Audi does not endorse the use of chemical

substances (leak inhibitor additives) for purposes of sealing

leaks in refrigerant circuits.

♦ Chemical substances used to seal leaks form deposits in the

refrigerant circuit. These can impair the function of the air con‐

ditioning system and cause the air conditioning system (and

your air conditioner service station ) to fail.

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♦ These chemical substances (leak stop additives) react mostly

with the ambient air or the humidity to stop leaks in the refrig‐

erant circuit. They cause deposits to build up in the refrigerant

circuit (and your air conditioner service station ), cause valves

to malfunction and defects in other components with which

they come into contact. These deposits cannot be completely

removed from the components (not even by cleaning/flush‐

ing). The refrigerant circuit can only be repaired by replacing

all components that have come into contact with this sub‐

stance.

1.4.2

Searching for leaks in refrigerant circuits

using an electronic leak detector

Special tools and workshop equipment required

♦ Electronic leak detector or proprietary device

Note

♦ Leaks in R1234yf refrigerant circuits can only be found using

electronic leak detection devices designed for R1234yf refrig‐

erant.

♦ The various refrigerants have a different molecular structure.

The sensors of electronic leak detection devices are adapted

to these molecules. If an electronic leak detection device is

used that is not designed for R1234yf refrigerant, it will not

respond to R1234yf refrigerant at all or only in larger concen‐

trations in the vicinity of the leak. For this reason, electronic

leak detection devices designed only for R134a refrigerant

cannot be used for leak detection in the R1234yf refrigerant

circuit.

♦ Depending on the type of heater and air conditioner unit, a leak

from the evaporator can be investigated by holding the test

probe of the leak detector against the glove compartment

cooler connection in the heater and air conditioner unit, or by

holding the test probe against the open condensation drain

connection of the heater and air conditioner unit with the con‐

densation drain hose pulled off.

Performing leak detection on a completely empty refrigerant cir‐

cuit caused by a leak:

Note

With a completely empty refrigerant circuit, proceed as follows to

ensure that no more refrigerant than necessary enters the envi‐

ronment during testing:

– Evacuate refrigerant circuit using air conditioner service sta‐

tion ⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

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Note

♦ If a larger leak is detected during the evacuation process, de‐

termine the cause and rectify as described

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

♦ If during the evacuation process no leak is detected or a very

small leak is detected that cannot be located using the vacuum

test, proceed as follows.

– If the refrigerant circuit is completely empty, charge the system

with approx. 10% of refrigerant and perform leak detection in

the same way as per a fully charged refrigerant circuit

⇒ page 70 .

Performing leak detection on a charged refrigerant circuit:

– Switch off ignition.

– Start the leak detector according to the operating instructions.

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– Always hold probe tip under location of suspected leak.

If, inherent of the design, the rate of clicks rises or a wailing noise

is heard, a leak has been detected ⇒ operating instructions for

leak detector .

Note

♦ Refrigerant gas is quickly dispersed by movement of air.

Draughts must therefore be avoided during leak detection.

♦ Refrigerant gas is heavier than air and therefore sinks at the

point at which it escapes.

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1.4.3

Searching for leaks with UV leak detec‐

tion system

Note

♦ Certain leaks are difficult or impossible to find using an elec‐

tronic leak detection device. To investigate these leaks, leak

detection can be performed using the leak detection system

⇒ Electronic parts catalogue .

♦ Refrigerant and refrigerant oil leaks out of the refrigerant circuit

when the circuit has a leak. This oil generally remains in the

vicinity of the leak location. To make the oil visible under^lU^kV

light, a small amount of fluorescent fluid must be added to the

refrigerant circuit. This fluid (PAG oil with an additive which

lights up under UV light) is injected into the refrigerant circuit

and distributed with the refrigerant oil when the air conditioning

system is switched on.

♦ The air conditioning system must be operated for at least

60 minutes to ensure that the injected leak detecting additive

is distributed throughout the entire refrigerant circuit (air con‐

ditioner compressor must run). The leak may become visible

under UV light after a short period, but this depends on the

size of the leak.

♦ The refrigerant oil with additive, which lights up under UV light,

can be added directly in an open circuit or charged after emp‐

tying the circuit with air conditioner service station via the

service connection.

♦ If the leak detection additive is added to the refrigerant circuit

via the service connection, a small amount of leak detection

additive will be deposited in the service connection. Carefully

remove any deposits so that this area is not mistaken for a leak

during subsequent leak detection.

♦ If a component from a circuit in which leak detection additive

is filled is renewed, thoroughly clean the connection points to

other components after assembling the refrigerant circuit. Dur‐

ing subsequent leak detection, deposits of leak detection ad‐

ditive could otherwise be mistaken for leaks at the connecting

point.

♦ When purging the refrigerant circuit, refrigerant oil and there‐

fore also leak detection additive also enter the air conditioner

service station . The refrigerant oil is separated from the re‐

frigerant in the oil separator of the air conditioner service

station and removed from the air conditioner service station

via the drainage outlet. The drained refrigerant oil may not be

reused. It must be replaced with fresh refrigerant oil.

♦ If leak detection fluid was injected during a previous repair of

the refrigerant circuit, observe the following: do not inject new

leak detection fluid unless the refrigerant machine oil has been

replaced. If only some of the refrigerant machine oil was re‐

placed then only the respective amount of leak detection fluid

should be injected. If, for example, 100 ml of refrigerant oil is

replaced in a vehicle with 250 ml of refrigerant oil, inject only

3

1 ml (cm ) of leak detection additive.

♦ Certain materials and their compounds (e.g. oxidisation prod‐

ucts on components made from aluminium, corrosion protec‐

tion wax, etc.) also light up under UV light.

1. Refrigerant circuit

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♦ Depending on the type of air conditioner service station , it can

also be used to add the leak detection additive directly into the

system. See the operating instructions of your air conditioner

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service station ⇒ Operating instructions air conditioner service

station .

Leak detection on an empty, leaking refrigerant circuit

– With a completely empty refrigerant circuit, proceed as follows

to ensure that no more refrigerant than necessary enters the

environment during testing:

– Evacuate refrigerant circuit with air conditioner service station

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

Note

If a larger leak is detected during the evacuation process, deter‐

mine the cause and rectify as described

⇒ “1.4.4 Detecting leaks in a vacuum test using air conditioner

service station , or in a pressure test”, page 77 and

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

If during the evacuation process no leak is detected or a very

small leak is detected that cannot be located during evacuation,

proceed as follows.

Note

♦ Only use UV leak detection additive approved for R1234yf re‐

frigerant.

♦ The leak detection additive contains refrigerant oil for the most

part. Since special refrigerant oils are required for R1234yf

refrigerant, only UV leak detection additives may be used that

use this oil as a carrier. UV leak detection additives developed

for R134a refrigerant are therefore unsuitable.

♦ For refrigerant circuits with R1234yf and R134a refrigerant,

different refrigerant oils (PAG oils) are used, which is why it is

important to ensure correct allocation of the leak detection ad‐

ditive (PAG oil with an additive that lights up under UV light).

♦ Charge the refrigerant circuit with UV leak detection additive

using the air conditioner service station ⇒ page 75 .

♦ Charge the refrigerant circuit with UV leak detection additive

using the leak detection system ⇒ page 75 .

– Charge the refrigerant circuit with the specified amount of UV

leak detection additive and the requisite amount of refrigerant

⇒ page 72 , ⇒ “2.6 Charging refrigerant circuit”, page 146

and ⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data .

– Run the air conditioning system for at least 60 minutes with

the air conditioner compressor switched on.

– Investigate leaks with UV leak detection system

⇒ page 75 .

Charge the refrigerant circuit with UV leak detection additive using

the air conditioner service station .

– Charge the refrigerant circuit with UV leak detection additive

and the requisite amount of refrigerant using air conditioner

service station ⇒ “2.6 Charging refrigerant circuit”, page 146

and ⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data .

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Note

♦ The amount of UV leak detection additive to be charged in the

3

refrigerant circuit with a refrigerant oil volume up to 150 cm

is 3.0 ± 0.5 ml. If the volume of refrigerant oil in the refrigerant

circuit is greater, more UV leak detection additive must be

added accordingly, e.g. 5.0 ± 0.5 ml in a refrigerant circuit with

3

a refrigerant oil volume of 250 cm . If the UV leak detection

additive is filled with an air conditioner service station , the

volume to be set in your air conditioner service station may

differ. Therefore, observe the relevant operating instructions

⇒ Operating instructions Air conditioner service station .

♦ For the specific volume of refrigerant oil in the refrigerant cir‐

cuit, refer to the vehicle-specific workshop manual ⇒ Heating,

air conditioning; Rep. gr. 00 ; Technical data .

♦ If leak UV leak detection additive was injected during a previ‐

ous repair of the refrigerant circuit, observe the following: do

not inject new UV leak detection additive unless the refrigerant

machine oil has been replaced. If only some of the refrigerant

machine oil was replaced then only the respective amount of

UV leak detection additive should be injected. If, for example,

50 ml of refrigerant oil is replaced in a vehicle with 150 ml of

3

refrigerant oil, inject only 1.0 ml (cm ) of UV leak detection

additive.

The leak detection system comprises the following parts:

♦ Cleaning agent -3-

♦ UV leak detection lamp -4-

♦ UV absorbing eye protection -5-

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♦ Sticker -6-

♦ Gloves -8-

Note

Items -1-, -2- and -7- in the diagram can be disregarded.

Special tools and workshop equipment required

♦ Leak detecting system

♦ Air conditioner service station with means of adding UV leak

detection additive in the refrigerant circuit ⇒ Electronic parts

catalogue .

♦ Approved leak detection additive ⇒ Electronic parts cata‐

logue .

– Evacuate the refrigerant circuit as per the instructions, and

charge the system with UV leak detection additive and refrig‐

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

⇒ “2.6 Charging refrigerant circuit”, page 146 .

– Wait until the pressures on the high pressure and low pressure

side have settled.

1. Refrigerant circuit

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– Detach the air conditioner service station from the refrigerant

circuit and switch off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

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– Attach a label close to the service connections that shows that

the refrigerant circuit has been injected with a UV leak detec‐

tion additive.

– Remove any remains of UV leak detection additive from the

service connection e.g. with absorbent paper, and clean the

area with cleaning agent - VAS 6201/3- .

– Seal the service connection with a cap.

– Bring the air conditioning system into operation.

– Run the air conditioning system for at least 60 minutes with

the air conditioner compressor switched on.

– Search for leaks in the refrigerant circuit using a UV lamp

⇒ page 75 .

Searching for leaks in refrigerant circuit using a UV lamp

CAUTION

Risk of eyes being dazzled by UV light.

– Wear protective goggles.

– Never glare into the UV lamp.

– Never point a UV lamp at another person.

– On vehicles with high-voltage system, switch off “stationary air

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conditioning” function (deactivate)⇒ Owner's Manual and ⇒

Operating instructions of infotainment/MMI .

– Switch off ignition.

1. Refrigerant circuit

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Note

♦ The air conditioning system must be operated for at least

60 minutes to ensure that the injected leak detecting additive

is distributed throughout the entire refrigerant circuit (air con‐

ditioner compressor must run). The leak may become visible

under UV light after a short period, but this depends on the

size of the leak.

♦ Depending on the size and location of the leak, it can take

several days until sufficient refrigerant oil with UV leak detec‐

tion additive has leaked out and the leak can be easily identi‐

fied as such.

♦ In the event of leaks at the evaporator, the additive may be

washed out with the condensate and emerge via the conden‐

sate drain. As the evaporator is not accessible on the majority

of models without a great amount of work, a check of the con‐

densed water drain point can indicate a leaking evaporator.

This does however require the additive to have been in the

refrigerant circuit for a lengthy period (several days).

♦ The protective eye wear is not only required to protect the

eyes. It also amplifies the illumination of the UV leak detection

additive under the UV lamp.

♦ Depending on how easy it is to reach various components in

the refrigerant circuit, it may be necessary to remove certain

parts from the vehicle (e.g. bumper or air filter).

♦ Only a small amount of refrigerant oil reaches certain areas of

the refrigerant circuit during operation of the air conditioning

system (e.g. a cap fitted at the top of a receiver installed on

the condenser). If there is a leak in these areas, it may take

quite some time before a sufficient quantity of refrigerant with

refrigerant oil and additive escapes at this point and can be lit

up under UV light showing where the leak is. At these points,

therefore, it may be more pertinent to search for a leak using

an electronic leak detection device

⇒ “1.4.2 Searching for leaks in refrigerant circuits using an

electronic leak detector”, page 69 .

– Position the vehicle in a darker area of the workshop (in day‐

light or under strong lighting the effect of the UV lamp is greatly

reduced).

– Check accessibility to various components of the refrigerant

circuit and remove parts in the vicinity of the refrigerant circuit

that obstruct the view of the refrigerant circuit components

(e.g. noise insulation and bumper).

– Protect eyes with safety goggles.

– Connect UV lamp to a 12 V battery (vehicle battery). Ensure

that the polarity of the connections is correct.

– Switch on the UV lamp and light up the components in the

refrigerant circuit. Positions at which refrigerant - along with

refrigerant oil and leak detection additive - can leak out fluo‐

resce (light-up) under UV light.

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1.4.4

Detecting leaks in a vacuum test using

air conditioner service station , or in a

pressure test

All vehicles

CAUTION

Risk of freezing injury caused by escaping pressurised refrig‐

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erant.

There is a risk of injury to the skin and parts of the body due to

freezing.

– Wear protective gloves.

– Wear protective goggles.

– Extract refrigerant and open the refrigerant circuit immedi‐

ately afterwards.

– If more than 10 minutes have passed since the refrigerant

was extracted, repeat the extraction process before opening

the refrigerant circuit. Pressure could build up in the refrig‐

erant circuit from continued evaporation.

– Switch off ignition.

♦ Detecting leaks in a vacuum test using air conditioner service

station , or in a pressure test

⇒ “2.5 Evacuating refrigerant circuit”, page 140

Note

♦ Smaller leaks in the refrigerant circuit (less than 100 g refrig‐

erant loss per year) cannot usually be found by means of the

vacuum test or pressure test. The amount of air entering the

system or the nitrogen-air escaping it is too low to detect the

faulty area through noise.

♦ It is also not always possible to detect leaks in the refrigerant

circuit with more than 100 g refrigerant loss per year by means

of the vacuum test or pressure test, depending on the envi‐

ronmental conditions (noise around the area, location of leak,

etc.). The air entering the system and nitrogen escaping it

could be too low to generate a noise that would be noticeable

in the faulty area.

♦ Larger leaks in the refrigerant circuit (e.g. more than 100 g

refrigerant loss per day caused by a stone hitting the con‐

denser) can be detected depending on the environmental

conditions, e.g. noise coming from the faulty area, which is

noticeable during the vacuum test or pressure test

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

– Perform vacuum or pressure test ⇒ page 143 .

1.4.5

Detecting leaks in a pressure test (with

nitrogen or compressed air)

♦ Perform a vacuum test using the air conditioner service station

to see if any leaks can be found

⇒ “2.5 Evacuating refrigerant circuit”, page 140 . If a leak can

be detected but not the exact location of the leak, an additional

pressure test can be performed using nitrogen or compressed

air ⇒ page 143

1. Refrigerant circuit

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Note

♦ Smaller leaks in the refrigerant circuit (less than 100 g refrig‐

erant loss per year) cannot usually be found by means of the

vacuum test or pressure test. The amount of air entering the

system or the nitrogen-air escaping it is too low to detect the

faulty area through noise.

♦ It is also not always possible to detect leaks in the refrigerant

circuit with more than 100 g refrigerant loss per year by means

of the vacuum test or pressure test, depending on the envi‐

ronmental conditions (noise around the area, location of leak,

etc.). The air entering the system and nitrogen escaping it

could be too low to generate a noise that would be noticeable

in the faulty area.

♦ Larger leaks in the refrigerant circuit (e.g. more than 100 g

refrigerant loss per day caused by a stone hitting_lkthe con‐

denser) can be detected depending on the environmental

conditions, e.g. noise coming from the faulty area, which is

noticeable during the vacuum test or pressure test

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

♦ A larger leak in the refrigerant circuit can be detected, for ex‐

ample, by pressurising the circuit to a maximum of 15 bar using

cleaned and dried compressed air or nitrogen ⇒ page 124 . If

the leak is large enough, the leakage point can be detected by

sound as the gas escapes.

Tools required:

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Refrigerant circuit -> 1.4 Investigating leaks for Your Volkswagen Scirocco SUV Third Generation (2008-2017)

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