Rear defogger not working

[Be_Jammin]

Hi, I'm having a bit of trouble with my rear defogger: I switched the tailgate on my hatchback for one with a window wiper, initially I though it was okay, as the window mounted light was working, but a couple days later I attempted to use my defogger and discovered otherwise.
To troubleshoot I did the following:
1) I checked the fuse; it's fine.
2) Verify the defogger was receiving electricity; around 12 volts across positive window tab to ground window tab.
3) Check the Bus for electricity; around 12 volts from one side to the other.
4) Check each parallel line for conductivity; most show around 12 volts, however a few do not.

This is was confuses me, since the strips are wired in parallel, shouldn't the defogger continue to work on the good lines? There is zero heat generated from any of the lines. :confused:

[Daxin]

hi, I am having the same issue. What am I missing to check?

[CoryM]

I've not looked closely at the Yaris defogger, but typically they will still work along the good lines so long as you have power and ground. You have checked the ground side?

[Bluevitz-rs]

The grids are long resistors, so you can check for volts across the lines. You should have about 0V with the system on across from one side to the other. If you're showing 12V, non of the lines are working and are all probably cut. You can actually check them along each line and get a different voltage reading if they're broken. Half way should be around 6V. The closer you get to the ground from the feed the lower the voltage.

Hopefully I didn't cock that up, it's been a while since I've had to check one. They used to make repair kits for them.

[Daxin]

I've used a Volt meter and got 12V on each of the lines. I've checked the relay on the Ecu and got a reading of 12V the switch is engaged. I don't understand how there is voltage on each line and not have the defogger work. I've checked the ground as well. There is voltage when touching the power end to the ground side.

[Bluevitz-rs]

So if you put the meter on each connector of the defogger grids you get 12V?

[Bluevitz-rs]

Red on one side black on the other

[Daxin]

Actually I get about 12.39 volts by touching the red end on the tab to the black end of the defogger tab.

[Bluevitz-rs]

What I'm getting at is its the same reading if you unplug the window grid? Plugged in the grid should use up all the voltage. If you're getting a reading then all the grid lines are broken.

[Daxin]

Sorry, I'm a little confused. When I take the defogger tab off the grid, there is no voltage when I test the two grids on either side, nor any voltage on any of the lines..

[CoryM]

If you have voltage and ground at the defogger the only things left are the defogger itself, lack of current, or magic. I've never looked on the Yaris, but some vehicles have a coating over the lines so you won't get any voltage if you try to measure on them.

The next step if you are certain it's not working is to unplug both ends of the defogger and jump power and ground straight from a battery. This will confirm whether or not the unit is working. It may take 5-10min to warm up enough to notice. If it is not working, repair or replace it. If it does work, you need to look for bad connections causing low current. The flex point in the hatch is a good area to start your search.

Cheers.

[Be_Jammin]

The grids area long resistors, so you can check for volts across the lines. You should have about 0V with the system on across from one side to the other. If you're showing 12V, non of the lines are working and are all probably cut. You can actually check them along each line and get a different voltage reading if they're broken. Half way should be around 6V. The closer you get to the ground from the feed the lower the voltage.

Hopefully I didn't cock that up, it's been a while since I've had to check one. They used to make repair kits for them.


It's been a while since I checked this but I believe all the lines had 6v at the halfway point. Plus I inserted an ammeter between the grid and ground and I believe it was showing 0.5 amps.

Has anyone replaced the rear windshield? How much was it?