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:
Changing a wheel
Fig. 170 Changing the wheel:
removing the wheel bolts with the screwdriver handle
First read and observe the introductory
information and safety warnings
Removing the wheel
Read the checklist .
Loosen the wheel bolts .
Jack up the vehicle .
Using the hexagonal socket ...
Improvised Tools
Note
This list outlines the testers, tools and materials required
for expert refrigerant circuit repair work.
Caution
Non-approved tools or materials such as leak sealing
additiv ...
Wear Spots
Wear spots are caused by a hard stop with locked wheels
whereby the rubber compound is abraded from the contact patch.
When the tires slide across the road surface, frictional
heat is generated which reduces the abrasion resistance on the
...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information