1996-2006 Volkswagen LT Van Checkingpressuresonvehicles -> 10.5 Checking systems with a restrictor and reservoir... User Manual
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Checkingpressuresonvehicles -> 10.5 Checking systems with a restrictor and reservoir... for Your 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  
10.4.3  
Specifications  
High-pressure side:  
Increasing from the pressure when the engine is stopped to a  
maximum of 20 bar positive pressure.  
Low-pressure side:  
Decreasing from the pressure when the engine is stopped to 1.3  
bar positive pressure.  
10.5  
Checking systems with a restrictor and  
reservoir and air conditioner compres‐  
sor regulating valve - N280- (with exter‐  
nally regulated air conditioner compres‐  
sor)  
Note  
♦ Connecting air conditioner service station ⇒ page 126 .  
lk  
♦ Observe the test prerequisites ⇒ page 127 .  
– Raise engine speed to 2,000 rpm.  
– Observe air conditioner service station pressure gauge.  
Note  
Switching pressures for the air conditioner compressor regulating  
valve - N280- and the radiator fan - V7- are vehicle-specific.  
⇒ Rep. gr. 87  
10.5.1  
Specifications:  
High-pressure side:  
Rising from starting pressure (when pressure gauge is connec‐  
ted) to 20 bar.  
10. Checking pressures on vehicles  
143  
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 - Low pressure (measured at the service connection) in bar ab‐  
solute pressure.  
B - Control current for the air conditioner compressor regulating  
valve - N280- .  
C - Permitted tolerance range.  
Note  
♦ Under unfavourable conditions (very high ambient tempera‐  
tures, high atmospheric humidity), the pressure on the high-  
pressure side can increase to a maximum of 29 bar.  
♦ The control current -B- is indicated in the measured values  
block.  
♦ The high pressure is indicated in the measured values block  
⇒ Rep. gr. 87 .  
lk  
♦ The low pressure is adjusted to within tolerances within the  
output range for the air conditioner compressor depending on  
the control current for the air conditioner compressor regulat‐  
ing valve - N280- .  
♦ Under unfavourable conditions (very high ambient tempera‐  
tures, high atmospheric humidity), the output may be insuffi‐  
cient to achieve the specification in every case.  
♦ The set working current for the regulating valve must be great‐  
er than 0.3 A to ensure that the regulating valve is reliably  
activated.  
♦ At the setting for “maximum cooling power”, the control current  
should be approx. 0.8 A (indicated in the measured values  
block) ⇒ Rep. gr. 87 .  
♦ Absolute pressure means that 0 bar corresponds to an abso‐  
lute vacuum. The normal ambient 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).  
144  
Rep. gr.00 - Technical data  
lk  
Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...  
Air conditioning system with refrigerant R134a - Edition 10.2014  
Possible deviation Possible cause of fault Rectifying fault  
from specification  
•
High pressure  
remains con‐  
♦ Actuation of air con‐ – Check ac‐  
ditioner compressor  
regulating valve -  
N280- is defective.  
tuation of air  
conditioner  
compressor  
regulating  
valve -  
stant or increa‐  
ses only slightly  
(above the pres‐  
sure measured  
when the engine  
is stopped),  
♦ Insufficient refriger‐  
ant in circuit.  
N280- .  
– Look for  
•
•
Low pressure  
falls quickly to  
the diagram val‐  
ue or lower,  
leaks using  
leak detector  
and rectify  
them.  
The required  
– Recharge re‐  
frigerant cir‐  
cuit.  
cooling output is  
not delivered.  
•
•
High pressure is  
normal,  
Low pressure  
matches the dia‐  
gram value,  
•
The required  
cooling output is  
not delivered.  
•
•
High pressure is  
normal,  
Low pressure is  
too low (see dia‐  
gram),  
•
The required  
cooling output is  
not delivered.  
•
•
High pressure is  
normal,  
Low pressure is  
too low (see dia‐  
gram),  
•
The required  
cooling output is  
not delivered.  
Note  
If no fault can be found for this complaint, purge (clean) refrigerant  
circuit with refrigerant R134a ⇒ page 67 . If this is not possible in  
your workshop, blow through refrigerant circuit with compressed  
air and dry with nitrogen ⇒ page 65 .  
10. Checking pressures on vehicles  
145  
Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...  
Air conditioning system with refrigerant R134a - Edition 10.2014  
Possible deviation from specifica‐  
tion  
Possible cause of fault  
Rectifying fault  
lk  
•
High pressure increases only  
slightly above the pressure  
measured when the engine is  
stopped,  
♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
♦ The air conditioner compressor is defective.  
•
•
Low pressure falls only slightly,  
– Purge (clean) refrig‐  
erant circuit  
The required cooling output is  
not delivered.  
⇒ page 67 .  
– Renew air condi‐  
tioner compressor.  
•
High pressure rises above spec‐ ♦ Restriction or obstruction in the refrigerant – Feel the refrigerant  
ification,  
circuit.  
circuit with the hand  
to sense the tem‐  
perature gradient.  
•
•
Low pressure falls only slightly,  
The required cooling output is  
not delivered.  
•
At one component a  
temperature gradi‐  
ent will be detected:  
– If a hose or pipe is  
kinked or crushed,  
renew it.  
– In case of an ob‐  
struction, blow  
through refrigerant  
circuit with com‐  
pressed air and ni‐  
trogen.  
•
If no faults are  
found:  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
•
High pressure and low pressure ♦ Moisture in the refrigerant circuit.  
are normal at first, but after a  
– Blow through refrig‐  
erant circuit with  
compressed air and  
nitrogen.  
while, the high pressure increa‐  
ses beyond the specification,  
•
•
The low pressure falls to the di‐  
agram value or lower,  
– Renew reservoir.  
– Repeat the check; if  
the system does not  
operate correctly  
The cooling power called for is  
not delivered.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Recharge refriger‐  
ant circuit.  
– Repeat check.  
146  
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 specifica‐  
tion  
Possible cause of fault  
Rectifying fault  
lk  
•
High pressure is normal,  
♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
•
Low pressure is too low (see di‐  
agram),  
♦ The air conditioner compressor is defective.  
•
The cooling power required is  
delivered.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Renew air condi‐  
tioner compressor.  
Note  
♦ If the fault is “high pressure normal, low pressure too low ” note  
the following: if faulty the evaporator could ice up or the re‐  
quired cooling output is not delivered.  
♦ In this case, the evaporator may ice up although the correct  
quantity of refrigerant is present in the refrigerant circuit.  
♦ Check the measured value of the evaporator output tempera‐  
ture sender - G263- or evaporator temperature sensor -  
G308- .  
♦ Check the actuation of the air conditioner compressor regu‐  
lating valve - N280-  
⇒ Rep. gr. 87  
Possible deviation from specifi‐  
cation  
Possible cause of fault  
Rectifying fault  
•
•
•
High pressure normal or too ♦ Too much refrigerant in circuit.  
high,  
– Extract some refrig‐  
erant from the refrig‐  
erant circuit.  
Low pressure too high (see di‐  
agram),  
•
The quantity of re‐  
frigerant extracted is  
about equal to the  
prescribed charge  
quantity:  
The air conditioner compres‐  
sor is noisy (especially imme‐  
diately after being switched  
on),  
– Renew the air condi‐  
tioner compressor.  
•
The required cooling output is  
not delivered.  
•
The quantity of re‐  
frigerant extracted is  
significantly greater  
than the prescribed  
charge quantity:  
– Recharge refrigerant  
circuit.  
– Repeat check.  
•
•
High-pressure and low-pres‐ ♦ Too much refrigerant oil in circuit.  
sure are normal,  
– Drain refrigerant cir‐  
cuit.  
The required cooling output is  
not delivered.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
10. Checking pressures on vehicles  
147  

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