1996-2006 Volkswagen LT Van Checkingpressuresonvehicles -> 10.6 Checking systems with an expansion valve, receiver... User Manual
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Checkingpressuresonvehicles -> 10.6 Checking systems with an expansion valve, receiver... for Your Volkswagen LT Van Second Generation (1996-2006)

lk  
Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...  
Air conditioning system with refrigerant R134a - Edition 10.2014  
Possible deviation from specifi‐  
cation  
Possible cause of fault  
Rectifying fault  
•
High-pressure and low-pres‐  
sure are normal,  
•
The air conditioner compres‐  
sor is noisy (especially imme‐  
diately after being switched  
on),  
•
The cooling power required is  
delivered.  
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 .  
10.6  
Checking systems with an expansion  
valve, receiver and air conditioner com‐  
pressor regulating valve - N280- (with  
externally regulated air conditioner com‐  
pressor)  
Note  
♦ Connecting air conditioner service station ⇒ page 126 .  
♦ 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 regu‐  
lating valve - N280- and the radiator fan - V7- are vehicle-  
specific.  
♦ Pressures should be measured at the service connections; the  
location of these connections is vehicle-specific ⇒ Rep. gr.  
87 .  
10.6.1  
Specifications:  
High-pressure side:  
Rising from starting pressure (when pressure gauge is connec‐  
ted) to 20 bar.  
148  
Rep. gr.00 - Technical data  
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  
lk  
block.  
♦ The high-pressure value measured by the high-pressure  
sender - G65- is indicated in the measured values block ⇒  
Rep. gr. 87 .  
♦ 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 “maximum cooling power”, the control current  
should be approx. 0.65 A to 0.8 A (vehicle-specific, 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).  
10. Checking pressures on vehicles  
149  
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 ♦ Actuation of air con‐ – Chelckk ac‐  
remains con‐  
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 di‐  
agram value.  
•
The required  
cooling output is  
not delivered.  
•
•
High pressure is • Insufficient refriger‐ – Extract some  
normal.  
ant in circuit.  
refrigerant  
from the re‐  
frigerant cir‐  
cuit.  
Low pressure  
too low (see dia‐  
gram).  
•
The quantity  
of refrigerant  
extracted is  
significantly  
less than the  
prescribed  
charge  
•
The required  
cooling output is  
not delivered.  
quantity.  
– Look for  
leaks using  
leak detector  
and rectify  
them.  
– Recharge re‐  
frigerant cir‐  
cuit.  
– Repeat  
check.  
•
The quantity  
of refrigerant  
extracted is  
about equal  
to the pre‐  
scribed  
charge  
quantity.  
150  
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 Possible cause of fault Rectifying fault  
from specification  
•
Expansion valve de‐ – Renew ex‐  
fective  
pansion  
valve.  
– Recharge re‐  
frigerant cir‐  
cuit.  
– Repeat  
check.  
Note  
♦ If no fault can be found for this complaint, purge (clean) re‐  
frigerant 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 .  
♦ Check the measured values of the evaporator output temper‐  
ature sender - G263- or evaporator temperature sensor -  
G308- and actuation of the air conditioner compressor  
regulating valve - N280- . If the measured value of the evap‐  
orator output temperature sender - G263- or the evaporator  
temperature sender - G308- is faulty, the evaporator may ice  
up or the cooling output will not be achieved.  
♦ If a repeat test after the expansion valve has been renewed  
indicates that the air conditioning system is still not operating  
correctly, refit the expansion valve and purge the refrigerant  
circuit with compressed air and nitrogen. Then renew the air lk  
conditioner compressor and receiver.  
♦ In this case, the evaporator may ice up although the correct  
quantity of refrigerant is present in the refrigerant circuit.  
♦ If the expansion valve is defective (always closed or not open‐  
ing wide enough) the air conditioner compressor regulating  
valve - N280- will be set to maximum power and the low-pres‐  
sure value will fall to the diagram value or less (the air condi‐  
tioner compressor is drawing the refrigerant out of the low-  
pressure side). However, since no refrigerant can flow through  
the expansion valve, the required cooling power is not deliv‐  
ered, and it can be that the high-pressure value does not rise  
at all or not enough, since no energy exchange is occurring.  
Possible deviation from specifica‐  
tion  
Possible cause of fault  
Rectifying fault  
•
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- .  
•
•
Low pressure falls only slightly.  
The required cooling output is  
not delivered.  
10. Checking pressures on vehicles  
151  
lk  
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  
♦ The air conditioner compressor is defective. – Extract refrigerant.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Renew air condi‐  
tioner compressor.  
– Recharge refriger‐  
ant circuit.  
•
High pressure increases be‐  
yond the specification.  
♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
•
•
Low pressure falls quickly to the  
diagram value or lower.  
The required cooling output is  
not delivered.  
♦ Restriction or obstruction in the refrigerant – Feel the refrigerant  
circuit.  
circuit with the hand  
to sense the tem‐  
perature gradient.  
•
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.  
– Recharge refriger‐  
ant circuit.  
– Repeat check.  
•
If no faults are  
found:  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Recharge refriger‐  
ant circuit.  
– Repeat the check; if  
the system does not  
operate correctly  
♦ Expansion valve defective.  
– Extract refrigerant.  
– Renew the expan‐  
sion valve and re‐  
ceiver.  
– Recharge refriger‐  
ant circuit.  
152  
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  
♦ In this case, the evaporator may ice up although the correct  
quantity of refrigerant is present in the refrigerant circuit.  
lk  
♦ If the expansion valve is defective (always closed or not open‐  
ing wide enough) the air conditioner compressor regulating  
valve - N280- will be set to maximum power and the low-pres‐  
sure value will fall to the diagram value or less (the air condi‐  
tioner compressor is drawing the refrigerant out of the low-  
pressure side). However, since no refrigerant can flow through  
the expansion valve, the required cooling power is not deliv‐  
ered, and it can be that the high-pressure value does not rise  
at all or not enough, since no energy exchange is occurring.  
Possible deviation from specifica‐  
tion  
Possible cause of fault  
Rectifying fault  
•
High pressure and low pressure ♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
are normal at first, but after a  
time the high pressure increa‐  
ses beyond the specification.  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
•
After a time, the low pressure  
falls to the diagram value or low‐  
er.  
•
•
The cooling power called for is  
not delivered.  
High pressure and low pressure ♦ Moisture in the refrigerant circuit.  
are normal at first, but after a  
– Extract refrigerant.  
longer drive, the low pressure  
– Blow through refrig‐  
erant circuit with  
compressed air and  
nitrogen.  
falls to below the specification  
(evaporator iced up).  
– Renew receiver to‐  
gether with dryer.  
– Evacuate refriger‐  
ant circuit for at  
least 3 hours.  
– Recharge refriger‐  
ant circuit.  
– Repeat the check; if  
the function is not  
OK  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Recharge refriger‐  
ant circuit.  
– Repeat check.  
10. Checking pressures on vehicles  
153  
Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...  
Air conditioning system with refrigerant R134a - Edition 10.2014  
Note  
♦ If this complaint occurs after a longer period of operation or  
only occasionally (the low pressure falls below the specifica‐  
tion and the evaporator ices up) it is sufficient only to renew  
the dryer (fitted within the receiver). Check the quantity of re‐  
frigerant oil. Then evacuate the refrigerant circuit for at least 3  
hours.  
♦ In case of this complaint, it is not initially necessary to purge  
the refrigerant circuit with compressed air and nitrogen, since  
as a rule only a small quantity of moisture will have accumu‐  
lated in the system, which can be removed by a longer evac‐  
uation period.  
lk  
♦ In this case, the evaporator may ice up although the correct  
quantity of refrigerant is present in the refrigerant circuit.  
Possible deviation from specifica‐  
tion  
Possible cause of fault  
Rectifying fault  
•
High pressure normal, low pres‐ ♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
sure too low (see diagram), the  
required cooling power is deliv‐  
ered.  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
♦ Expansion valve defective.  
– Extract refrigerant.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Renew the expan‐  
sion valve and re‐  
ceiver.  
– Recharge refriger‐  
ant circuit.  
– Repeat the check; if  
the system does not  
operate correctly  
– Renew the air con‐  
ditioner compres‐  
sor.  
♦ The air conditioner compressor is defective. – Extract refrigerant.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Renew the air con‐  
ditioner compres‐  
sor.  
– Recharge refriger‐  
ant circuit.  
– Repeat check.  
154  
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 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.  
lk  
♦ Check the measured values of the evaporator output temper‐  
ature sender - G263- or evaporator temperature sensor -  
G308- and actuation of the air conditioner compressor  
regulating valve - N280- . If the measured value at the high-  
pressure sender - G65- is faulty, the evaporator can ice up or  
the required cooling power is not delivered.  
♦ If the defect is in the air conditioner compressor regulating  
valve - N280- (the regulating valve is not activated, but the air  
conditioner compressor still runs), it is not necessary to blow  
through the refrigerant circuit. If this fault occurs, it is sufficient  
to renew the air conditioner compressor (check the refrigerant  
oil quantity in the air conditioner compressor).  
♦ If the expansion valve is defective (always closed or not open‐  
ing wide enough) the air conditioner compressor regulating  
valve - N280- will be set to maximum power and the low-pres‐  
sure value will fall to the diagram value or less (the air condi‐  
tioner compressor is drawing the refrigerant out of the low-  
pressure side). However, since no refrigerant can flow through  
the expansion valve, the required cooling power is not deliv‐  
ered, and it can be that the high-pressure value does not rise  
at all or not enough, since no energy exchange is occurring.  
⇒ Rep. gr. 87  
Possible deviation from specifi‐  
cation  
Possible cause of fault  
Rectifying fault  
•
•
•
High pressure normal or too ♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
high.  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
Low pressure too low (see di‐ ♦ Too much refrigerant in circuit.  
agram).  
– Extract some refrig‐  
erant from the refrig‐  
erant circuit.  
The air conditioner compres‐  
sor is noisy (especially imme‐  
diately after being switched  
on).  
•
The quantity of re‐  
frigerant extracted is  
about equal to the  
prescribed charge  
quantity:  
•
The required cooling output is  
not delivered.  
– Renew the air condi‐  
tioner compressor.  
•
The quantity of re‐  
frigerant extracted is  
significantly greater  
than the prescribed  
charge quantity:  
– Recharge refrigerant  
circuit.  
– Repeat check.  
10. Checking pressures on vehicles  
155  
lk  
Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...  
Air conditioning system with refrigerant R134a - Edition 10.2014  
Possible deviation from specifi‐  
cation  
Possible cause of fault  
Rectifying fault  
♦ Too much refrigerant oil in circuit.  
– Drain refrigerant cir‐  
cuit.  
•
The quantity of re‐  
frigerant extracted is  
about equal to the  
prescribed charge  
quantity.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Recharge refrigerant  
circuit.  
– Repeat check.  
♦ Expansion valve defective.  
– Drain refrigerant cir‐  
cuit.  
– Renew the expan‐  
sion valve and re‐  
ceiver.  
– Recharge refrigerant  
circuit.  
– Repeat the check; if  
the system does not  
operate correctly  
– Renew the air condi‐  
tioner compressor.  
♦ The air conditioner compressor is defective. – Drain refrigerant cir‐  
cuit.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Renew the air condi‐  
tioner compressor.  
•
The quantity of re‐  
frigerant extracted is  
significantly greater  
than the prescribed  
charge quantity.  
– Recharge refrigerant  
circuit.  
– Repeat check.  
156  
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 defect is in the air conditioner compressor regulating  
valve - N280- (the regulating valve is not activated, but the air  
conditioner compressor still runs), it is not necessary to blow  
through the refrigerant circuit. If this fault occurs, it is sufficient  
to renew the air conditioner compressor (check the refrigerant  
oil quantity in the air conditioner compressor).  
♦ 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 .  
♦ If the expansion valve is defective (always closed or not open‐  
ing wide enough) the air conditioner compressor regulating  
valve - N280- will be set to maximum power and the low-pres‐  
sure value will fall to the diagram value or less (the air condi‐  
tioner compressor is drawing the refrigerant out of the low-  
pressure side). However, since no refrigerant can flow through  
the expansion valve, the required cooling power is not deliv‐  
ered, and it can be that the high-pressure value does not rise  
at all or not enough, since no energy exchange is occurring.  
Possible deviation from specifi‐  
cation  
Possible cause of fault  
Rectifying fault  
•
High pressure and low pres‐ ♦ Actuation of air conditioner compressor reg‐ – Check actuation of  
sure are normal.  
ulating valve - N280- is defective.  
air conditioner com‐  
pressor regulating  
valve - N280- .  
lk  
•
The required cooling output is ♦ Too much refrigerant oil in circuit.  
not delivered.  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
•
•
High pressure and low pres‐ ♦ Too much refrigerant oil in circuit.  
sure are normal.  
– Drain refrigerant cir‐  
cuit.  
The air conditioner compres‐  
sor is noisy (especially imme‐  
diately after being switched  
on).  
– Purge (clean) refrig‐  
erant circuit  
⇒ page 67 .  
– Recharge refrigerant  
circuit.  
•
The cooling power required is  
delivered.  
– Repeat check.  
♦ Expansion valve defective.  
– Renew expansion  
valve.  
10. Checking pressures on vehicles  
157  

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