On a 2000 Ford Windstar, the engine block heater cord is typically located
on the passenger side of the engine block, near the bottom. It's often a heavy-duty cord with a plug that will be visible once you look at the lower portion of the engine compartment on the passenger side. You might need a flashlight to see it clearly.
However, it's not always in the exact same spot on every vehicle. Some minor variations in placement can occur due to manufacturing tolerances or even minor modifications. If you can't find it easily, consulting your owner's manual (if you have it) is a good idea. It should have a diagram showing the location.
