Pontiac Repair: Window Defrosting, rear defogger, south elgin high school

Question
My name is Ryan, I am a student at South Elgin High School and we are doing a project in our engineering class. We have to come up with an idea to solve a problem and we our trying to  make an easier way to defrost your car window. Do you see this as a real problem? And do you have an suggestions?

Answer
Hi Ryan:

it is an issue here where I live in the North east. we use it pretty regularly from November thur march. The only real issue with the system is that it crated a pretty hefty draw on the electrical system which in turn makes the alternator work harder and it can adversely effect fuel mileage. Back in the advent of defroster all there was was a fan mounted on the rear package shelf that blew air from the trunk onto the back Glass needless to say it didn't work so well.
I have an idea for you if you had a current sensing rear defogger or a moisture senor on the glass to limit that time and the defogger would run or the moisture sensor saw that the glass was clear then it would turn it off. some cars are just on a timer it will run for "X" amount of time or they have a fancy system that it will only run for "X" amount of time but if the system see a certain vehicle speed it will keep it on constantly.

if you know anything about electricity that the less resistance in a ckt. the more current flows thus the heat. More resistance less current flow less heat. the resistance of the back glass grids changes and the glass warms up you could have a temp sensor on the glass that once it gets to a certain temperature the current is turned down even more. You could have it run as a duty cycle less of a cycle less current. more of a duty cycle more current.

Hope that helps you out.

Feel free to ask anything else. If you get a patent on my idea i get a cut ;)