Hello to the forum, first time poster. My names Brad. Ive got a 2001 caravan with the dual zone climate control that Im having some troubles with. Ive searched quite a bit, and theres some great advice on here for finding and replacing the blend door arm, and the heater core, but I havent been able to find how to diagnose the problem anywhere.
I have read that with the dual zone, it is usually on one side (mostly passenger), as there is an actuator for each zone. I have no heat from either side. if my switch is on the off position, I get heat trickeling from the vents, but as soon as I turn the fan on, the heat disapears and blows cold. Both the water lines heading to the heater core from the engine bay have heat. Any help would be greatly apreciated

 

http://i55.tinypic.com/i754ww.jpg

the steps for the test are at the top of the image

 

Welcome to DF
I would replace the thermostat first, unless the cooling system is low. The t-stat maybe stuck open and that is why you are not getting any heat.