i experience the same thing with my ,05 i dont use the climate control feature as i see it as counter productive to have the a/c compressor running full time and then adding heat to maintain the selected temperature, so i manually turn it on and off.

and have noticed that if the a/c has not been used for a while ( a few days) then it can be slow coming on, however if i use it as designed it works every time.

i just wish that you could set a minimum temp. and the compressor would kick in and out to maintain that temp.

my wife had a Citroen for a short time (got rid of it as it was a piece of dog poo) and the a/c in it seemed only to want to work on cool days, it was a stupid car

i,m not a big fan of climate control as it is in these cars. especially with fuel prices being what they are, it seems stupid to run an a/c compressor robbing the car of power and consuming extra fuel and then adding heat to achieve the desired temp, why not just cut the compressor in and out like in times past