Test And Measurement Work That Can Be Performed Using A Pressure Gauge - Volkswagen Amarok 2011 Workshop Manual

Amarok 2011 ➤ , Beetle 2012 ➤ , Bora 1999 ➤ , CC 2010 ➤ , CC 2012 ➤ , ...
Air conditioning system with refrigerant R134a - Edition 10.2014
Note
In vehicles with air conditioner compressor regulating valve -
N280- , the pressure on the low-pressure side is varied by acti‐
vating the valve.
2.9 Test and measurement work that can be
performed using a pressure gauge
Displays on the pressure gauge
1 - Temperature scale for refrigerant R134a CF3–CH2F or
CH2F–CF3.
2 - Pressure scale
In addition to the pressure scale, the pressure gauges can have
one or more temperature scales. The scale values for R134a are
assigned according to the vapour pressure table. Because differ‐
ent refrigerants have different vapour pressures at the same
temperature, each temperature scale is labelled for the respective
refrigerant.
2.9.1 Pressure gauges enable the following
test and measurement work
a – Pressure and temperature measurement in the refrigerant cir‐
cuit
♦ The high-pressure gauge allows the pressure and tempera‐
ture to be measured with the air conditioning system switched
on irrespective of whether this is at the outlet of the air condi‐
tioner compressor through the condenser up to the restriction
(restrictor or expansion valve).
♦ The low-pressure gauge allows the pressure and temperature
to be measured with the air conditioning system switched on
irrespective of whether this is at the restriction (restrictor or
expansion valve) through the evaporator up to the inlet to the
air conditioner compressor.
Note
The relationship between pressure and temperature shown on
the pressure gauge is valid only where the refrigerant in the circuit
is liquid or vapour, but not when it is gas. In the gaseous state,
the temperature is approx. 10°C to 30°C higher than indicated on
the pressure gauge.
b– Evidence of refrigerant in a closed container
Refrigerant R134a is present in a closed container or refrigerant
circuit if the temperature indicated on the pressure gauge corre‐
sponds to the temperature of the refrigerant (the temperature of
a standing liquid stabilises at ambient temperature).
A closed container or switched-off refrigerant circuit is empty if the
temperature indicated on the pressure gauge is below the tem‐
perature of the refrigerant.
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Rep. gr.00 - Technical data