5KCSTQW rear window defroster

[Ameer Antar]

This is a pain to work on, but it's real important. Just disconnect the 
ground and 12V line going to the glass. Measure ohms of each strip [very 
end to very end]. Compare.

There's no paint that is only conductive or resistive, it's all relative. 
The paint is a bit conductive and also a bit resistive. It's like 'is the 
glass half full or half empty?' But the more paint there is the lower the 
resistance, the less paint, the higher the resistance. The paint must have 
been cut or worn somewhere. On the strips that read near infinite ohms, 
these are the bad strips. Move the test leads next to each other and move 
one of them away until you have a sudden [non-linear] jump in resistance. 
[You can calculate how much ohms per inch of paint on a good strip.] The 
point where the resistance jumps is the break. Verify by moving the other 
lead next to that point and make sure you still get near infinite 
resistance across the break. Actually it might not be a break, just a worn 
away portion which has very high resistance like 100k ohms. This high 
resistance slows the current down quite a bit and the strip won't heat. Be 
careful of how you test the strip, b/c placing the test leads on it hard 
can break away more paint, causing more problems as you go. Be very gentle. 
The paint can be found at any decent car parts place...napa, advance auto, 
pepboys, etc. good luck.

-ameer


At 05:30 PM 11/27/2000 , you wrote:
>Rear defroster fails to function.
>1. Switch good
>2. 12V all the way to the bus that feeds the network of conductive elements
>crossing the glass.
>3. Good ground all the way to the bus collecting electrons from the
>elements.
>4. O Volts on each element 50 mm out into each element from the ground side
>5. Measure from the positive side, some traces have voltage almost all the
>way across, but measure 12 V. One trace measures approximately 3 volts at
>3/4 of the way across from the positive side (this one works as I expect,
>though it's broken).
>
>I expected these resistive elements to work like a printed resister
>potentiometer. Thus, they would all measure some reduced voltage above
>ground when measured at some distance from the positive bus. Alas, only one
>seems to show any voltage drop at all. None of the elements carries any
>voltage all the way across the window.
>
>I might attempt to use the conductive bridging paint suggested in other
>posts, but that seems like it would only work for the one trace that
>actually shows a voltage drop. All the others seemingly have had all the
>resistive element scrubbed off, leaving a conductive trace underneath. This
>seems unreasonable, since I expect the traces to be a single resistive
>material applied during the manufacturing process.
>
>What am I missing? Anyone know where I can acquire actual resistive paint,
>rather than conductive, to repaint the whole resistive strip? Any other
>solutions out there rather than replacing the whole window ($500 from
>Nationwide).
>
>Paul Meyers
>Gray 87 5KCSTQ 1.8bar eurolights fuchs 145 kM, needs loom transplant
>Pearl 88 5KCSTQ 1.8bar eurolights fuchs bilsteins 125 kM 2pc-em k24 turbo
>Metallic White 87 5KTQW eurolights bilsteins 191 kM daily driver
>Blue 86 5KCSTQ parts car