Volkswagen Polo Service & Repair Manual: Critical Point
| Vehicle air conditioning systems make use of the
vaporization and condensation process. In this case, one works
with a substance which boils easily, designated as refrigerant. |
| The refrigerant employed is tetrafluoroethane R134a, which
boils at -26.5 °C (-15.7 °F) at a vapor pressure of 1 bar (14.5
psi). |
| The critical point (critical temperature and critical
pressure) is that above which there is no longer a boundary
between liquid and gas. |
| A substance above its critical point is always in the
gaseous state. |
| At temperatures below the critical point, all types of
refrigerant in pressure vessels exhibit both a liquid and a gas
phase, i.e. there is a layer of gas above the liquid. |
| As long as there is still gas present in the container next
to the fluid, pressure is dependent on ambient temperature.
Refer to
→ Chapter „Refrigerant R134a Vapor Pressure Table“. |
 Note
| Different types of refrigerant are never to be mixed. Only
the refrigerant designated for the corresponding A/C system may
be used. |
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Vehicle air conditioning systems make use of the
vaporization and condensation process. In this case, one works
with a substance which boils easily, designated as ref ...
Vehicle air conditioning systems make use of the
vaporization and condensation process. In this case, one works
with a substance which boils easily, designated as ref ...
Other materials:
Removing and fitting head restraints
First read and observe the introductory information
and safety warnings
Every seat is fitted with a head restraint. The centre rear head restraint is
designed solely for use with the centre rear seat. This head restraint should therefore
not be installed in any of the other positions.
Remov ...
Switching the TCS on and off
Fig. 116 In the centre console: button
for switching the TCS on and off manually
First read and observe the introductory information
and safety warnings The electronic stability control (ESC) only
functions when the engine is running. It consists of ABS, EDL and TCS.
When the engine is r ...
Repairs and technical modifications
First read and observe the introductory information
and safety warningsRepairs and modifications must always be carried
out according to Volkswagen specifications .
Unauthorised modifications to the electronic components or software in the vehicle
may cause faults. As the electronic componen ...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information