YJBrian

To close the loop, shortly after posting this, the noise stopped along with the defrosting. I checked the fuse and the relay and all was good, but the defroster never heated up on any of the three windows panes. I sat on this until recently where after diagnosis, the dealer said the sliding glass had no power and the entire window assembly needed to be replaced. I am out of the factory warranty, so the dealer contacted GM and got some assistance on the repair, costing me $450 for a 'deductible' and it was replaced the next day. Thankfully it did not shatter like some of you experienced and I could deal with it on my time. Unfortunately, they had no other information on the fault and I did not take a much closer look to see if there was evidence of melting/burning in areas that others have posted photos of before I brought it in for repair.

The issue seems intermittent as the noise is not present every time the defroster is turned on, at least in my case. I have kids in the back as well and I would hate for the window to pop when they are in the truck with me. Does anyone have a wiring diagram or other information on the defroster circuit through the window assembly? I have not taken a hard look at it, but it looks like the path through the window may be hidden in the trim.

I'm experiencing a similar issue in my 15 Sierra. I can hear the buzzing/sizzling noise, and so far no smoke or broken glass, so I'm not using the defroster to avoid further issue. Is the cause if the failure known? I'll bring it by the dealership, but the truck is out of the bumper to bumper warranty at this point, so I'm not expecting much. Buzzing is definitely related to the defroster and it goes away when the rear window is opened, but it does not seem to be coming from the electrical contacts to the sliding window. In my case, it sounds more like it is from the drivers side window.