The rear defroster seems to be working poorly. The dash switch lights up when pressed, the relay in the fuse box works, and defogger fuse (40 A) is OK. The grid measures 1 ohm, the grid in good condition, and the ground connections on the inside of the hatch are tight. I've cleaned the battery ground connection and the body ground lead on the driver side front fender. The ground lead between the battery and the body on the driver side front fender reads 0.1 ohms. I see supply voltage (13.3 V) across the grid connection with the engine on and the rear defroster dashboard switch on.

The rear defroster appears to draw about 15 A based on using a 1 ohm shunt replacing the fuse. Is this the normal draw for the rear defroster? The grid resistance alone with a supply voltage of 13 V should show 13 amps. The rear defogger is on a 40 A fuse.

If I run a heavy cable between the battery ground back to the hatch area, and I measure the resistance between the hatch ground and the battery ground, I get 15 ohms. I am puzzled by this reading. I would expect that to be a lot lower, like a few ohms at most. To me, this suggests that there's some bad ground connection somewhere in the body.