You may have a small pinhole in the radiator that leaks slow, and when the ac fan is on, its blowing the coolant off the bottom of the radiator. When the fan is off, it probabally just builds up a little and falls off when driving. (When you cannot notice it).
Also, are you certain it's coolant and not just water? Where is the coolant actually coming from? Have you seen it coming from the radiator?
Or do you just notice a wet patch under the car. It's possible the heat exchanger is leaking (the radiator in the heater box) and leaking out through the A/C drain tube.
Get the coolant system pressure tested to confirm the location of the leak.
Could even be a bad transmission cooler or cooler hose, it runs to radiator and uses same coolant.
Wednesday, June 9th, 2010 AT 8:38 PM