What would cause a 1994 Mazda mx6 to heat up fine when it is at a idle but then cools down to no heat at all when driving?

Answer 1

Air moving through the radiator cools the coolant which cools the engine. Even without the fan, if you are driving in cold temperatures the result can be very dramatic on the temperature of your coolant (and engine). Car manufacturers are more worried about overheating than about cabin temperatures (same coolant goes thru your heater core) and they usually sell the same cars in all climates. Here is an old Michigan winter trick: try putting cardboard or some type of tarp or bra in front of the radiator. Watch your temperature gauge, though. It it starts getting too hot you might want to make it smaller or cut a hole in it to provide more air.