2005 Outback Rear Window Defogger is not working

[rubbernut]

Help to solve this mystery!
Both fuses are OK, side mirrors are working as they should, timer on switch is working and disconnects in 15 min, relay is clicking, everything seems to be ok except rear defogger is dead! Fuse 22 has 14.2V on it and responds to switch position. Grid on the rear door is not damaged.

[plain OM]

Fuse 22? That is the fuse for the rear defogger relay energizing coil. I believe the main fuse for the defogger power that is switched by the relay is #10 in the engine compartment fuse box. It should have power on both sides when the defogger switch is turned on (for the 15 minutes).

Anything else in the rear gate (hatch) not working or not working properly? (License plate lights, back-up lights, high stop light, wiper, rear gate door lock/unlock).

There have been cases of broken wires going to the rear gate. The power wires for most of the electrical functions in the hatch go through the rubber, accordian-like boot at the upper right of the door opening. (The boot at the upper left has the washer fluid hose, wiring to the radio antenna amplifier, and a ground wire.) Because of the repeated flexing, and the way the boot and wires are oriented, the wires inside tend to break. It's not uncommon to find more than one function not working properly.

Here's a small selection of threads dealing with the issue. Some have pics, some have details of repair, and there are further links in some:

Hatch lock failure?

05 Hatch lock problem.

Rear Wiper Does Not return to Park or Home Position

Third Brake light and License lights out - most of the time

[rubbernut]

Thank you, Plain OM. Your point is correct, My mistake. Fuse #10 is under the hood and #22 is under the dash. #10 is responding to the switch input with 14.2V on both leads in "on" position and with 0V in "off" position. Timer also works fine (turns the circuit "off" in 15 min). All functions in hatch are working as they should (both license plate lights, both back up lights, third brake light, window wiper, door lock) except defogger and it is the most frustrating part. Wires bundle in the rubber booth on the right are looking sparkling new w/o visible cracks of breaks.

[plain OM]

Okay, so all the main electrical supplies are working.

It's very rare that a problem arises in the fixed wiring harnesses that go from the front area to the back. (Perhaps one exception is when mice get in and chew on the wires, typically in the engine area.) In many cases the breaks in the wires in the flexible boot aren't visible because the wires (there's about 15) are bundled together, and those inside the bundle can't be seen. In addition, part of the wire bundle going through the rubber boot is wrapped, which also hides broken wires. In some of the other threads dealing with this problem, pulling on the wires where they are accessible often resulted in one or more coming out of the bundle. confirming that it was broken inside. The defogger uses two wires going through the boot, and if only one is cracked, the defogger won't work.

Also, have you checked for continuity across the defogger grid? Looking for visible damage, unless examined closely, might not reveal a crack, or cracks in the printed traces. The connections to the grid are on sides under the interior trim at the sides of the window. The trim can be pulled off to expose the terminals where the wiring connects to the grid. One of the linked threads has some related photos.

Worst case, you might have to pull off the interior trim in the cargo area to access the connectors between the "rear" wiring harness, and the "door" harness that goes through the boot to the rear hatch. It would then be possible to check for the voltage at the connector, leaving the door harness.

[rubbernut]

Just as you suggested: breaks in the fixed rear harness (passanger side). See attached image:

[plain OM]

Thanks for the follow-up. Appears there's more than one broken wire, which suggests that other electrical functions in the rear hatch probably stopped working, or working properly, since the defogger failure became apparent.

Let us know what you do to repair them and how it turns out.