LS400 rear window defroster lines

[Brybo86]

so on my 1995 Lexus LS400 I noticed that there is a spot where the defroster isn't working.

I haven't had an issue with the rear defrost on any car before

there are two leads on the drivers side middle of the window, they look fine.
From what I can guess from the pic there must be some kind of break either on 3 of the lines or maybe just the 1 line in the center of the strip of snow.

I carefully looked inside and I don't see any obvious breaks in the line....? can I use a multimeter to test these?

For the expert out there does the power come from the sides or the middle?
(the snow looks to be melting from the middle out)
unless that is because when driving the snow is being blown up on the sides?

 

[razel]

Power comes from the leads. Most that I've seen are from the side, perhaps yours is in the middle. Also if your car doesn't have a whip antenna, usually the top most lines is the antenna. You can definitely check the continuity with a multimeter to determine what's broke and which is antenna and defroster.

I attempted once to fix the defroster lines on my car. It was the type you paint on. It didn't last very long. In fact, in my case the entire defroster lines on the windows were just disintegrating. I ended up taking it to a repair shop. Not sure what did. It was the original window still, so I assume they just used industrial defroster magic whateverz.

 

[Kestas]

The procedure for finding the breaks requires a voltmeter. I forget the exact details, but they should be available with a bit of Google searching. I've used it before. The procedure tells you where along the length of line the break is located.

 

[zzyzzx]

I just think you have more snow on that side, since those lines seem to be working no the right side.

Either that or break out a pair of 3X reading glasses and inspect those lines.

 

[AandPDan]

Originally Posted By: zzyzzx
I just think you have more snow on that side, since those lines seem to be working no the right side.


I agree. The line either works all the way across or not at all. It looks like just some snow slid down on the left side of the picture.

 

[Brybo86]

No the only part that doesn't work is the small section in the pic with snow on it

 

[Rick in PA]

I just fixed a couple of broken lines on my rear window defroster, here's what I found / did.

The circuit was +12 volts on one side, ground (0 volts) on the other. Take a multimeter and set it to volts DC. Ground the one lead of the multimeter. Take the other lead of the multimeter and touch the line on the window when the defroster is activated (they are conductive):

A good line will produce a smoothly changing voltage gradient from +12 volts on one side to 0 volts on the other side. There will be about 6 volts at the center.

A bad line (one with a break) will produce some odd voltage on the line. In my case, it was about 10.5 volts. As I worked my way across the line it displayed a constant 10.5 volts. At some point on the line, the voltage suddenly dropped to, lets say, 1.5 volts. Where the voltage suddenly changes is where the break in the line is.

Put a piece of tape near the break to mark it. Clean the break with alcohol. Put two short pieces of tape, just above and just below the line to mask it. Scan it with the multimeter probe to find the exact location of the break and put a small mark on the tape where the break is.

Get out your conductive paint. They have defroster repair kits at auto parts stores. Mix / shake the paint well, the conductive fillers settle. Apply a dab of paint over the break. I'd recommend applying a second coat of the conductive paint. Allow to dry and carefully remove the masking tape. It should work.

My car has the lines all the way across with no vertical line in the center. I suspect the vertical line in the center just electrically bonds the lines together so a break only affects one side. That's why the defroster line does work on the right side.