2003 Jaguar X-Type A/C BLOWING HOT WHEN I SLOW DOWN OR STOP

I HAVE A 2003 jAGUAR X-TYPE AND AS LONG AS THE CAR IS GOING DOWN THE ROAD THE A/C WORKS, HOWEVER WHEN I SLOW DOWN OR COME TO A STOP IT BEGINS TO BLOW WARM AIR? WHAT IS THE PROBLEM...THANKS