Rear Window Defrost Problem

[markheth]

I am having a problem with my rear window defrost... I am getting a 12V power at all of the lines, but it is not working (not defrosting at all).

Anyone else experience this before?

[NISTECH]

when you say you had 12v at all the lines how did you test it?

[MaineExport]

What year car is it?

I'm not sure about the s13... but on the s14 not all of those lines are defroster coils. The lower half and one of the upper lines are actually a secondary radio antenna.

If it's not defrosting at all... then I can't imagine it's getting power. How did you test it?

[89240sx]

You also need to check to make sure there are no breaks in the defroster lines.... see FSM on how to repair! It's actually very easy to do

Also did you check voltage at the window? (I'm sure you did but I still need to ask)

[markheth]

I used a mini voltage line tester, with a sharp end on it. I poked several of the lines going through (since I have tinting on top), and they all lit up the test light. I didn't actually verify that I had 12V+ going through it, but the light was bright, so I assumed it was the case.

I also did a visual inspection of all the connections and lines, and they looked good to me.

It is a 1989 240SX (S13? what is the difference, I haven't seen it reffered to as a S13 or S14 yet).

Again this morning frost on the rear window, that didn't go away from the defroster

[89240sx]

That doesnt make any sense if you have voltage at the window but the frost is not going away ... Check your switch =\ ???

[NISTECH]

you need to use a volt meter and do a voltage drop check across the glass. one lead on the ground side and work your way across the glass. since your whole window is not defrosting just pick one line and work your way across. what you should see is this. black lead on glass ground tab and the other one less then an inch out on the wire approx. .5 to 1 volt and as you go across the voltage should increase till you hit the hot tab and see battery voltage. this would be registering a fully functional defroster.

[markheth]

Ahh. after a bit more looking into it, I found the problem.

It seems that the ground that goes through the drivers side of the hatch top, was completely worn right through (broke completely in half).

It makes sence that the test light worked, because I was in fact creating a ground for it.

The antena that goes through that hole was totally worn in half as well, so I repaired both of them by running new wire through it.

I checked the other side, and most of the wires on the other side (wiper motor controls and washer pump, power for defroster), were almost broken as well... Just a thread or so left on each wire.

Guess the hatch gets used alot! Well, after an hour or so of replacing wires, I think i'm all set. I tested everything, and the back window gets warm now!

It was working most of the time, and it must of been on the edge of not making contact anymore...

Anyhow, nice to have it all working again