Refrigerant under charge symptoms

Compressor run time excessive,

Compressor thermal overload trip,

Mechanical damage to compressor due to oil breakdown caused by excessive heat.

Compressor short cycling on low-pressure switch.

Reduction in capacity of system leading to product temperature rise

High Discharge Temperature

Expansion valve may form a ball of ice, it may also make a hissing noise and

the evaporator may ice up partially

Sight Glass would show bubbles although this is not an accurate indicator

The condenser may be unnaturally cold

Suction pressures may show up as low or possibly high if the expansion valve

is fully open.

Be careful of systems such as air driers fitted with hot gas bypass

valves, as these will have to be isolated from the system before accurate

readings can be taken.

Head pressures may be excessively low although again any means of head

pressure control used should be taken into account