itmustbeslim

Hello! I am new to this forum and reltively new to pathfinders! I have a 2006 LE 4X4. Recently noticed that the car will not blow warm air when the heater is on if the car is not moving, which is frustrating because it is ass cold here in WI right now. First spot I checked was coolant resovoir which was fine, then I checked the radiator, which was low. I added coolant to the radiator and immediately noticed drips underneath the skid plat right underneath the radiator. The heater does work fine when moving. The drips continued for a few dys and I have not seen any new drips a week later. How do I find the leak or in the alternative is my radiator cracked? If it is cracked it should not be a big deal to replace and besides, it'll allow me to bypass the cooler and hopefully avoid the stupid transmission repair (fingers crossed). If you do not think it is the radiator do you guys have any known culprits for leaks? Do any of you have a diagram of the radiator and all the connections? Thanks so much for your help