Rear defogger dead - does anyone have a wiring diagram

[billmcc64]

Hi all,

as the title says the rear defogger is dead in my wife's 1998 corolla.

When I push the defogger button, i can hear the relay click and the indicator on the dash comes on. But the defogger does not heat up.

So I checked the 2 fuses in the dash and they are both good.

I pulled off the rear trim panels by the rear window and the main lead is still connected to the defogger. The ground lead is also connected. There is no voltage on the hot lead when i turn on the defogger.

I checked the continuity at the rear window to make sure it wasn't a bad solder joint.

I noticed that the dash light did not come on when I turned the defogger on and I had the 40 amp main fuse out. I think this means that the relay is good, since the dash light seems to be energized only when the relay is on. And the dash light works when the 40 amp is in.

sigh.

so my best guess is that the main wire is broken somewhere, hopefully in the dash and not in the rear fender (which was replaced after a fender bender).

does anyone know where the defogger relay is in the dash? a wiring diagram would be a major assist here!

thanks for any help.!!!!

Bill

[cupidstoy]

sorry, can't help much more. you tried all the things i would suggest.

can you trace down the wire any where under the dash or in the trunk to determine the color/striping? my guess is that the wire doesn't run under the rear fender but instead runs along the driver or passenger door kick plate and under the back seat and up into the rear speaker area somehow. it's pretty easy to pull the rear seat bottom cushion and check if you know what color you're looking for. otherwise, i'd guess it's one of the thicker wires as it's supplying a decent amount of power to the rear defogger. if you can trace it down, you can check it along the way with a probe to see where the break is.

if i was guessing, i'd say maybe the rear seat clamps pinched it or it got cut somewhere on a sharp piece of metal frame as it was snaking around in the body tracks to get back there.

good luck.

[nhparrot]

Originally Posted by billmcc64

Hi all,

as the title says the rear defogger is dead in my wife's 1998 corolla.

When I push the defogger button, i can hear the relay click and the indicator on the dash comes on. But the defogger does not heat up.

So I checked the 2 fuses in the dash and they are both good.

I pulled off the rear trim panels by the rear window and the main lead is still connected to the defogger. The ground lead is also connected. There is no voltage on the hot lead when i turn on the defogger.

I checked the continuity at the rear window to make sure it wasn't a bad solder joint.

I noticed that the dash light did not come on when I turned the defogger on and I had the 40 amp main fuse out. I think this means that the relay is good, since the dash light seems to be energized only when the relay is on. And the dash light works when the 40 amp is in.

sigh.

so my best guess is that the main wire is broken somewhere, hopefully in the dash and not in the rear fender (which was replaced after a fender bender).

does anyone know where the defogger relay is in the dash? a wiring diagram would be a major assist here!

thanks for any help.!!!!

Bill

The DEF relay is on the inner circuit side of the Instrument Panel J/B (behind the 40A DEF fuse)

[billmcc64]

that's awesome guys. I'll check it out and let you know what happened.

thanks muchly,

Bill

[billmcc64]

that wiring diagram was a big help.

I checked the voltage at the floor wire and instrument panel connector and it was good.

so I followed the wiring harness all the way back to the rear window and it looked ok.

i took a closer look at the connector on the rear window, and it was all melted up. i figure the connection wasn't good, so it got hot enough to melt the connector, and the melted plastic completely broke the circuit.

soldered the wire onto the connector directly, problem solved.

Bill