Southbound

I have a 2006 silverado 1500 ext cab... I just had the front windshield replaced in the truck and that night going into work the heat only works at half power... Its works on all speeds but only blows like 50% or so... Anyone have any ideas what is going on? Should I call windshield place? I am just wondering if they set something at a setting or pulled a fuse to make it work like that so cab of truck doesn't build up pressure... I dunno thanks Will L