Ford Repair: Ford Explorer Compressor, ford explorer sport, dehumidfier

Question
I have a 2001 Ford Explorer Sport 4.0 V6.  My problem is when the HEATER is on and I stop at a red light or just idle in park the AC compressor keeps cycling on and off about every 5 seconds.  When the compressor clutch kicks in it draws the RPMs down to 100 or less.  When it shuts off the RPMs go back to normal.  It has even stalled a couple times.  If I turn off the heater it runs fine. Any Suggestions?

Answer
Hello Marty, It is normal for the compressor to come on when the heater mode is selected, The a/c works as a dehumidfier and makes a drier heat to clear quicker and keep down on mildew in the case. If it cycling quickly it may be low on freon. The stalling at idle may be something else. Hope this helps Thanks Tony