Chrysler Repair: Dodge grand caravan 1999, dodge grand caravan, grand caravan

Question
Hi Roland
My question is about over heating, my van has 98,000. miles radiator seams to be fine no leaks ,just put in a new thermostat .
when i put the ac on it starts to run hot so i turn it off and run the heat and it drops back to normal, all fluids are fine and full, again no leaks , no water in oil!!
and the fans work to, I just don't get it any ideas, or suggestions

Answer
Hi Robert,
I wonder if the air flow thruough the fins of the radiator migth be blocked with leaves or mud. Place a light behind it and see if you can see through it.
Another possibility is that the radiator tubes are partially blocked. See whether the manifold on each end of the radiator is about equal temperature to one another. Look in the filler opening to see if the flow through looks active. It one manifold is cooler than the other or the flow looks sluggish, then a rediator flush out would be in order.
Are you sure the gauge is accurate? Have you let the temp rise to H, but not had any boil off?
Those are the main possibilities. Let me know what you find.
Roland