Get Checkingpressuresonvehicles -> 10.3 Checking systems with an expansion valve and reservoir... Guide for Volkswagen LT Van Second Generation (1996-2006)

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...

Air conditioning system with refrigerant R134a - Edition 10.2014

Note

♦ Overfilling with refrigerant oil can occur if the refrigerant oil

level was not checked after the air conditioner compressor

was renewed.

♦ If the air conditioner compressor is not to be replaced, drain

refrigerant oil from air conditioner compressor via the drain

plug. From the total amount of refrigerant oil, fill 50 g direct into

air conditioner compressor and fill remainder in refrigerant cir‐

cuit according to ⇒ vehicle-specific workshop manual .

10.3

Checking systems with an expansion

valve and reservoir (with internally regu‐

lated air conditioner compressor)

Note

♦ Connecting air conditioner service station ⇒ page 126 .

♦ Observe the test prerequisites ⇒ page 127 .

– Raise engine speed to 2,000 rpm.

– Observe manifold gauge.

Note

The switch pressures and the versions of switches in the refrig‐

erant circuit are vehicle-specific.

Pressures must be measured at the service conne^lc^ktions; the fit‐

ting locations of these connections are vehicle-specific.

⇒ Rep. gr. 87

10.3.1

Specifications:

High-pressure side:

Rising from starting pressure (when pressure gauge is connec‐

ted) to maximum 20 bar.

10. Checking pressures on vehicles

135

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...

Air conditioning system with refrigerant R134a - Edition 10.2014

Low-pressure side:

Falling from starting pressure (when pressure gauge is connec‐

ted) to diagram value.

A - High pressure in bar positive pressure.

B - Low pressure in bar positive pressure.

C - Permitted tolerance range.

lk

136

Rep. gr.00 - Technical data

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...

Air conditioning system with refrigerant R134a - Edition 10.2014

Possible deviation

from specification

Possible cause of fault

Rectifying

fault

•

High pressure re‐ Too little refrigerant in cir‐ – Extract

mains constant or cuit or expansion valve

some re‐

frigerant

from the

refriger‐

ant cir‐

cuit.

increases only

defective.

slightly (above the

pressure meas‐

ured when the en‐

gine is stopped),

•

Low pressure falls

quickly to the dia‐

gram value or low‐

er,

•

The

quantity

of refrig‐

erant ex‐

tracted is

about

The required cool‐

ing output is not

delivered.

equal to

the pre‐

scribed

charge

quantity.

– Renew

expan‐

sion

valve.

– Recharge

refriger‐

ant cir‐

cuit.

– Repeat

check.

•

High pressure is

normal,

•

The

quantity

of refrig‐

erant ex‐

tracted is

signifi‐

Low pressure

matches the dia‐

gram value,

lk

cantly

•

The required cool‐

ing output is not

delivered.

less than

the pre‐

scribed

charge

quantity.

– Look for

leaks us‐

ing leak

detector

and recti‐

fy them.

– Recharge

refriger‐

ant cir‐

cuit.

– Repeat

check.

10. Checking pressures on vehicles

137

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...

Air conditioning system with refrigerant R134a - Edition 10.2014

Note

If no fault can be determined and the function of the air condi‐

tioning system is not OK when the test is repeated, purge refrig‐

erant circuit with refrigerant R134a (clean) ⇒ page 67 . If thi_ls_kis

not possible in your workshop, blow through refrigerant circuit with

compressed air and dry with nitrogen ⇒ page 65 .

Possible deviation

from specification

Possible cause of fault

Rectifying

fault

•

High pressure

rises above speci‐

fication,

♦ Restriction or obstruc‐ – Feel the

tion in the refrigerant

circuit.

refriger‐

ant circuit

with the

hand to

sense the

tempera‐

ture gra‐

dient.

Low pressure falls ♦ Expansion valve de‐

quickly to the dia‐

gram value or low‐

er,

fective.

•

The required cool‐

ing output is not

delivered.

•

At one

compo‐

nent a

tempera‐

ture gra‐

dient will

be detec‐

ted:

– If a hose

or pipe is

kinked or

crushed,

renew it.

– In case of

an ob‐

struction,

purge re‐

frigerant

circuit

with com‐

pressed

air and ni‐

trogen

and re‐

new ex‐

pansion

valve.

•

If no

faults are

found:

– Purge

(clean)

refriger‐

ant circuit

⇒

page 67 .

– Repeat

check.

138

Rep. gr.00 - Technical data

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...

Air conditioning system with refrigerant R134a - Edition 10.2014

Note

If the air conditioning system is still not operating correctly after

the refrigerant circuit has been purged with compressed air and

nitrogen, the expansion valve must be renewed.

lk

Possible deviation from specification

Possible cause of fault

Rectifying fault

•

High pressure and low pressure ♦ Expansion valve defective.

– Examine the expan‐

sion valve for dirt or

corrosion; renew if

necessary.

are normal at first,

♦ Moisture in the refrigerant circuit.

•

After a while, the high pressure

increases beyond the specifica‐

tion, and the low pressure falls to

the diagram value or lower,

– Blow through refrig‐

erant circuit with

compressed air and

nitrogen.

•

The cooling power called for is

not delivered.

– Renew receiver.

– Repeat the check; if

the system does not

operate correctly

– Purge (clean) refrig‐

erant circuit

⇒ page 67 .

– Recharge refriger‐

ant circuit.

– Repeat check.

Note

When this fault occurs, always renew receiver.

10. Checking pressures on vehicles

139

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...

Air conditioning system with refrigerant R134a - Edition 10.2014

Possible deviation from specification

Possible cause of fault

Rectifying fault

•

High pressure normal or too high ♦ Too much refrigerant in circuit.

– Extract some refrig‐

erant from the re‐

frigerant circuit.

(see diagram),

♦ Expansion valve or air conditioner com‐

pressor defective.

The required cooling output is not

delivered.

•

The quantity of re‐

frigerant extracted

is about equal to the

prescribed charge

quantity.

The air conditioner compressor is

noisy (especially immediately af‐

ter being switched on),

– Renew expansion

valve.

– Recharge refriger‐

ant circuit.

– Repeat test.

lk

•

The quantity of re‐

frigerant extracted

is significantly

greater than the

prescribed charge

quantity.

– Recharge refriger‐

ant circuit.

– Repeat check.

Note

If the air conditioning system is still not operating correctly when

the test is repeated, refit the expansion valve and purge the re‐

frigerant circuit with compressed air and nitrogen. Then renew the

air conditioner compressor and receiver.

Possible deviation from specification

Possible cause of fault

Rectifying fault

•

High pressure increases only

slightly above the pressure

measured when the engine is

stopped,

♦ The air conditioner compressor is defec‐ – Purge (clean) refrig‐

tive.

erant circuit

⇒ page 67 .

– Renew the air condi‐

tioner compressor

and receiver.

•

Low pressure falls only slightly,

The required cooling power is not

delivered.

Possible deviation

from specification

Possible cause of fault

Rectifying

fault

•

High pressure is ♦ Expansion valve or air – Renew

normal,

conditioner compres‐

sor defective.

expansion

valve.

Low pressure is

too low (see dia‐

gram),

– Recharge

refrigerant

circuit.

•

The cooling pow‐

er required is de‐

livered.

– Repeat

check.

140

Rep. gr.00 - Technical data

Checkingpressuresonvehicles -> 10.3 Checking systems with an expansion valve and reservoir... for Your Volkswagen LT Van Second Generation (1996-2006)

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