The manual for my 96 ETC says that when the rear defogger button is pushed, the system will operate for 10 minutes and shut off. Normally that is the case as i have timed it. But recently I noticed that it has been shutting off prematurely. At first I was thinking maybe a loose wire or a bad fuse but when I started to notice the problem I also began timing how long it would actually stay on. Then just this morning I went to turn it on and about 1 minute later it shut off. With the exception of what happened to this morning, it will either shut off after 10 minutes or exactly 5. It has yet to fail to turn on when I need it but it's strange how the timing just happened to cut in 1/2 like that. It does not do this all the time as when i used it last week everything was normal. ANYONE???????

Thanks guys