Rear Window Defogger Mystery Module

[TheGreyHearse]

The rear window defogger stopped working on my 2011 OB Premium w/winter package. It was repaired under warranty but the dealer tech found that the wiring for the rear defogger did not match the service manual diagrams - he found a vented plastic covered module where the correct colored wires entered and wires colored differently from the service manual diagram emerged to the rear window grid. The tech called Subaru to ask what this module might be (he could see what appeared to be a coil of heavier gage wire inside through the vent holes of the module). Subaru had no clue. My guess is that this is a ballast resistor for a circuit serving the rear window, the rear-view mirrors and the windshield wiper heat. Anyone have a clue?

[jogosub]

Possible remedy.
Locate the fuse for this component in the fuse box; see if it's OK; if not, replace the fuse with higher amps rating and see, it it works.

[hallux]

Originally Posted by jogosub

Possible remedy.
Locate the fuse for this component in the fuse box; see if it's OK; if not, replace the fuse with higher amps rating and see, it it works.

Then watch the car burn as the wires are asked to carry more current than they're rated for. The circuits are rated based on the wiring and the devices on the circuit, too much current on a wire is just asking for the insulation to melt and cause a short or fire.

The rear defroster should be powered through a relay, the "on" signal should command the relay to close and send power over bigger wires to the defroster grid.

[jogosub]

Hmmmm - I don't think so. Wires are ALWAYS heavier gauge than what they carry. It's a built in safety found in every automotive, aviation or space application. I have worked in those industries for many years.
I thought the poster said: defogger (and not defroster) - not that it would make any significant difference as they perform the similar or same duty.

[plain OM]

There's nothing in the power line to the rear gate (hatch) window defogger.

Where is that plastic-covered module? Is it in the rear gate, above the window? If it is, then it's the radio antenna amplifier.

The radio antenna amplifier has wires coming in (signal, power) from the body, and wires going out to the grid on the glass, so it could look as if it's connected to the defogger grid, but isn't. (There's two separate set of grid wires on the rear window -- the radio antenna, and the defogger.)

[TheGreyHearse]

Plain OM - You're probably figured it out for me. I didn't see the module or wiring myself but the Subaru Tech did mention Yellow/Black wiring coming out of the module which matches the color code from my service manual for the goesinta-goesouta wiring of the antenna amp. I give him a call to check this out and maybe teach both of us something. The original problem with my defogger was repaired by soldering a connector back to the grid.

[Saint J VT]

When I had my inner panels of the rear gate off, I saw that little black rectangular box, about half the size of a pack of cigarettes.

I thought it might be a homing-device.
That is, until I followed the wires.