You are on the way home from work and it's 92° outside. The temperature gauge is right in the middle where it belongs and the A/C is blowing plenty of cold air. All of a sudden traffic slows to a creep. Little by little the temperature gauge is rising to the HOT side of the gauge and the A/C is no longer pumping out cold air. In fact it is now the same temperature as the outside air. To keep from overheating you shut the A/C off. But to add insult to injury, you have to turn the heater on full blast to keep the radiator from blowing it's top and you open the sunroof and all the windows and wait for a breeze that never comes to cool you off.

Then you pass the accident on the side of the road that every driver on the road has to slow down and see and you are cruising again. The needle drops down a bit and you are no longer in imminent danger of overheating. Drenched with perspiration you turn on the A/C and even though it's not as cold as before, it's good enough to keep you from biting the cats' head off when you get home.