I was leaving a friend's house the other night. As I was backing out, I turned on the defroster. There was a very loud squeal, and then the brakes got very hard. I limped home with barely any braking power, and parked the car. Is there some connection between the defroster and brakes via the vacuum system? How do I troubleshoot this problem?

P.S. Power front disk brakes
TIA, Kevin

Split in the vacuum hose to the booster, could have made the squeal too.

Thanks Leo,

The AC was making the squeal prior to brakes going out. What else should I check besides the vacuum line to the booster?