When on low speed i get cold air. If i turn the blower up to full i dont and when the car speeds up it reduces the fan speed by its self.

Ive recently had the aircon regassed and no issues were raised when that was done.

What might be the issue?

Bit of an update to which you may have an answer.

 

This evening its Ice cold and working full whack all the time.

 

Does the aircon system have some kind of thermostat which might be faulty and causing it not to work when the outside temp is too high?