Dodge Repair: sporadic unexplained overheating-frustrated!!, dodge caravan, intermitently

Question
1998 Dodge Caravan
In early July, the a/c began working intermitently and the temp gauge kept going up accordingly. Took for a/c servicing and got repairs: front expansion valve, receiver/dryer and a/c service.  Then a week later, temp gauge went up again, they replaced the cooling fan relay.  Then last week which it has been about 5 weeks later, the a/c started working intermitently and the temp started going up again.  Last week they replaced the relay again.  A day later the a/c started working intermitently again and the temp went up.  They sent me to the Dodge Dealer to get the computer flashed from a TSB No: 18-33-97.  I was informed that the PCM was updated already and no updates were available.  Funny thing is when they left it idle with the a/c on full blast for 1 HOUR the temp never went up.  I came home and now 4 days later, every day it goes up when idling at a traffic light and the a/c is on.  If I shut off a/c and turn on heat, open windows, temp goes down to normal.  Then if I turn the a/c back on it will be fine again.  It seems there is a short somewhere.  Please help!  The dealer won't do anything until they can see the temp go up and it only does it sporadically.  Thanks for any help you can give..........

Answer
The problem is not with the a/c system it is with the overheating.  
if the car is overheating the a/c will not work. you need to make sure the radiator is full and clean. also make sure that when it starts to overheat is the fan running?  there was a problem with the fan relays on a lot of caravans.

Also you may have a thermostat that is sticking . this is a very cheep repair and may be cheeper then getting the dealer to check the other things.

Good luck
steve