Lights on but no one is home. . Rear defroster.

[2006GrayXLT]

It's been getting down to the 30*s and when I turn on the rear defroster nothing happens. I do not have a owners manual to I do not know what fuse to check. Thanks!

 

[Scorpion8]

Watching this. Mine does the same, but one of the grid connection tabs has been "iffy". I've re-epoxied it twice and slathered it with copper conductive paint, and it even appears to have 12V across it when energized but the defroster grid never seems to do anything.

 

[Explorer_PL]

Mine is completely broken off, I tried soldering it in but still no luck.
With the defroster lines, it's not enough that you have a light on the tester. You need to measure the voltage across the window.

 

[Scorpion8]

You need to measure the voltage across the window.

Any idea what the proper voltage across the grid should be in the range of?

 

[2006GrayXLT]

Bump

 

[Rcflyer330]

The proper voltage should be 12v across the grid. I had both tabs broken off and the grids broken in spots spent around the same amount of money on trying to repair them for 3 years or so that I could have bought a brand new ford rear glass. And in the end I replaced the rear window. For cost it was around $500 for a brand new rear glass panel from ford installed.

The problem is the glues and line repair paint dont last. Every time I needed to clean the rear window it would break the grid lines and the glue for the tabs would not hold for more than a year.

I was using the repair stuff from the autoparts store made by permatex. frostfighter.com sells a two part epoxy for tab repair but I dont know how well it works they also have a guide on diagnosing grid problems.

 

[Explorer_PL]

Rc

The voltage drops across the grid, 12v at one end, around 6v in the middle.
With current I constant, the Resistance R increases, and V decreases. R generates heat.

V = I x R

 

[2006GrayXLT]

Is there a fuse that runs the defroster?

 

[Rcflyer330]

Yes, it's a 40A fuse in spot 15 in the engine compartment. The defrost indicator light is a 15A in spot 13 under the dash in the drivers foot well.

also I just noticed you said you don't have a owners manual you can download one from ford.
Here is a link to the site Find Your Owner Manual | Official Ford Owner Site

 

[Explorer_PL]

Same like Rc, I tried to fix it numerous times, but the glue and the repair kits don't hold. I was thinking of getting a glass from a junk yard.

 

[2006GrayXLT]

I checked the fuse under the hood and it was good.

 

[2006GrayXLT]

How can you test and see if it works or not?

 

[Rcflyer330]

A volt meter or test light across the grid is one way. Another is spray a light mist of water on the back window when its on and see if lines appear in the water.

 

[2006GrayXLT]

Where does the defroster get its ground? Drivers side wire?

 

[Rcflyer330]

Drivers side wire is the ground.

 

[2006GrayXLT]

What wire is hot on the passenger side? Btw thanks for the help?

 

[2006GrayXLT]

Ok found the problem. Passenger side wire came off of the glass. How do I reattach it?

 

[Rcflyer330]

Check out this thread
Rear Window Defogger

I also stated in an earlier post what you can use and problems i had with the permatex stuff.

 

[Scorpion8]

I think both of my tabs are firmly attached, but the grid still doesn't work. I once measured 12V across the grid. Befuddled for sure.

 

[Rcflyer330]

With a volt meter check the voltage in the middle of the grid it should be around 6 volts check every bar from both sides. by both sides I am saying one lead to the large bar on the drivers side the other in the middle and repeat with one lead on the passenger side bar. another thing you could check is the resistance from the tab to the bar on each side it should be low. a tip to prevent more damage from the volt meter probe is to use aluminium foil on the probe tip that you are using on the small lines.