Whenever I turn on the A/C of my pick-up, I just noticed that the coldness varies on the time of the day specially now that it is summer. on medium A/C from 10am - 4pm, it is not that cold. but from 5pm onwards, it becomes cold. I actually turn the A/C to low because of the coldness.

my question is, are there any problems with the A/C system of my car? is flushing the answer to the problem? or adding freon?

thanks for the reply