In vehicle air$-$conditioning system, there are two ways of charging the refrigerant which being used to cheek the amount of refrigerant in the system. However, the most common method is to use a manifold pressure gauge to read high and low sides pressure of refrigerant. A Mercedes Benz C$200$ air conditioning system has been diagnosed by using a manifold pressure gauge to analyse its performance. As shown in Figure $1,$ during the inspection, manifold gauge pressure for both sides were showing very high value of pressure and most of the time were not stable especially at the high$-$pressure side.

Figure $1$: Manifold Gauge Reading

a$)$ List all requirements after connecting a manifold gauge to the air conditioning system before performing the refrigerant pressure testing.

$(6$ marks$)$

$($CLO$2$:PLO$5$:C$1)$

b$)$ Explain the causes of the problem and what are the methods can be performed in order to solve it$.$

$(14$ marks$)$

$($CLO$2$:PLO$5$:C$2)$