Answer:There's no switch in the radiator. The low coolant level sensor in the coolant expansion tank is intended to be the sole signal that activates the message at the Vehicle Information Center ...

I'm not sure what the oil level sensor was, but it was bolted onto the side of the oil pan, so it can't have been terribly complex. Why don't more vehicles have these devices?

Parts won't be available to install the coolant-level sensor until later this year. In the meantime, Ford will send letters to owners telling them how to check coolant and add some if it gets low.

Ford says it will repair any coolant leaks that might be found in more than 200,000 recalled vehicles that are at risk of catching fire.