Measure voltage & ground at connectors on rear window. Let's see if power is making it to window on one connector and is grounded on other one.

Also what is resistance across fuse legs?

 

Hi,
Where would the connectors be on the rear window?

 

The defog indicator light coming on means all the fuses (GAUGE, DEFOG, DEFOG-I/UP), defogger relay and defogger switch are working. That leaves wiring to the rear window. (This is based on my 97 wiring diagram.)

The connectors should be on the left and right side of the back window. Right side is grounded to a point on the right quarter pillar under the plastic. Left side should have the 12v when switch is on.

 

Thank you .I'll check later and report back.

 

Your rear defogger is probably performing like it's supposed to - they just doesn't work very well unless you run the AC compressor in conjunction.

Without the AC, mine barely makes a mark in the fog. My old '90 Corolla was the same way, but the AC didn't work, so I don't know if it would've worked in conjunction with AC.

Does your AC work?

 

Yea my a/c works.I think like you said the defroster works just not good. So are you saying run the a/c with defroster?

 

Yes. It doesn't matter if you're using heat or cooling, the running AC compressor will make the evaporator core cold, and the air rushing through the core will give up its moisture as it passes through. That moisture condenses on the cold core, (just like the outside of a cold beverage) and drips out of the HVAC box.

So in the winter, when you would be running heat and maybe directing it at the windshield, you can go ahead and push the button and turn on the compressor. The air will still come out hot, but it will be dryer, and will evaporate the fog quicker.

And the AC will strengthen the efforts of the electric grid in the rear window.

 

I'd think it should work enough to notice even without the AC on. The AC definitely works better for the front windshield (compared to just heat)

 

The defrosters in the rear windshield fail over time. The last time I seen a failure was on a 92 Tercel. It had failed on one side of the window. Never looked into it, but when there's a small break in the line, it will stop working.

If the test fails with the dmm, suspect the grids are bad and possibly replace the window.

 

It's unusual for a break to occur on big main branch, so most of time, if entire defroster's out, it's usually wiring leading up to it.

Most of time, it's single trace that breaks. You can tell because when defrosting, there's single line of fog that's not clearing.You can get little bottles of copper paint to repair broken traces on rear defroster. So I look very, very closely at that trace to find the break. Once identified, I gently sand 2-3mm on either side of break with 400-grit sandpaper to expose fresh copper. Then paint a line over break using the copper repair paint.

yeah, a little meticulous, but it really does work and I've had windows where I've had to repair each and every line over the years!