I recently did a RT KIX - HKG in a 744 but have expereinced this in a 343 also -

It is apparently the policy to not utilize AC in the rear of the aircraft on the ground.. In the first case above on 506 the temp rose to unbearable and dangerous levels in the cabin. The cabin staff was completely ineffectual in resolving the matter. It is unhealthy and dangerous to trap humans in that type of condition. In the US it is illegal to treat animals that way yet CX seems to persist in dealing with Coach passengers in this manner. These two flights are my last. I consider flying CX and the treatment I received to be dangerous to my health. Not everyone can tolerate these poor conditions and treatment. I dont carry a thermometer but it had to exceed 38 C !

As an economic move to have to save money by not providing ground AC or firing up an additional AC APC via the APU is a terrible way to save. ANA, NW, JAL and UA all use the same aircraft as CX and they can manage to not make passengers suffer like this.

These are my last CX flights.