Rear defrost doesn't work.

[987687]

Rear defrost on my 98 Legacy GT limited stopped working almost a year ago. It's been pissing me off for a while now.

It's one of the ones with a momentary button and a timer. Why it needs all that complicated crap is beyond me.

 

But anyway, it won't work. I changed the button with one I know works. And nothing. I don't hear the relay under the dash clicking, the light on the button doesn't light up.

 

If I apply power directly to the rear defrost it actually works. So it's some of the stupid electronics in the middle.

 

What do I need to do to fix it?

 

Oh, and before someone asks. No fuses are blown.

[987687]

Nobody?

[JPX]

I kind of have the same thing going on with my 1996 Legacy sedan. Ever since the rear window was replaced, the defrost does not work.

 

However, in my case, the relay does click when the switch is turned on. But I do not get power at the glass grid. So something in between is playing hard-to-get.

 

The relay is located just behind the OBD port on the left side of the dash - pretty much behind the hood release lever. You might want to check that out.

 

See if you can test the on the bench - actuating the coil side to see if it clicks. then check continuity on the contacts when the coil is engaged.

[1 Lucky Texan]

dunno how many fuses are involved or where they'r located. But, you need to hear the relay click so, once you've tried a different relay(the coil could be bad) it's time to trace the circuit (wiring/fuses) from the switch.

 

If the relay is switching and the contacts aren't burned off (try a different relay) then the circuit from there to the back , as well as the ground for the defroster (this could be in the harness that gets flexed so much from the hatch to the body - might be a bad wire???) , all needs to be traced out.

 

There are repair kits for cuts in the defroster traces themselves, if that is part of the problem.

[987687]

The defrost lines are fine. I've put power directly to it, and it works fine.

I'll have to check the relay, I had no idea where it was, hopefully mine is in the same place as JPX's.

 

JPX: The defrost in your car works different from mine. Yours is a toggle, when the button is pushed in, yours is always on. Mine is a momentary button, so it's on a 10min timer, then it shuts off.

[Cougar]

If you don't already own a test light probe that is used to verify where power is getting to I suggest you purchase one so you can do some testing with it. Using the probe, verify power is getting to both sides of fuse 7 in dash panel. That fuse supplies power to the relay contacts for the heater grid. Also verify power is getting to fuse 1 and fuse 15 in the same panel. Power for the relay coil is bridged from there and fuse 15 supplies power to the timer. If those things are okay then you can try swapping the relay in the fuse panel with one of the others near it. I think they are all the same. If that doesn't help then the switch circuit isn't working for some reason. Since the relay coil is turned on by a making a ground connection you should be able to ground the blk/blu wire tied to the fuse panel on pin f14 and turn on the relay. That will verify the switch circuit is at fault. My first suspect for the trouble would be a broken wire in the door jam. To see if that is the case, locate the timer module and ground the blue wire going to the timer. If that turns on the relay then the blue wire to the switch has a break in it. If that doesn't turn on the relay then the timer may be at fault. Use your probe to verify power is getting to the module on the red/blk wire.

 

The timer circuit is really for a safety. Many folks would forget about the circuit being on after it is switched on. The circuit draws a good amount of power and leaving something like that on all the time wouldn't be a good thing.

Edited May 31, 2012 by Cougar