Rear defrost electrical

Hi, I am new to this forum and the Jeep world.

I am running into issues with not getting any power to my rear defrost. The connection to the hardtop appears clean, the light on the switch lights up when defrost is turned on. When I attach a voltmeter to the defrost it does not appear to be getting any juice.

Does anyone have any ideas what the issue could be? I am trying to locate some kind of fuse diagram online for an 88 YJ but have had no luck so far, that shows any kind of defrost fuse.

Thanks