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Thu Sep 09, 2010 8:52 pm

I hate to contribute with another rear defroster post to add to the many that are here, but I am hoping this one will disseminate some of what has been written and also follow thru to a successful, useful answer.

Over the past few days, I have been skimming forum discussions regarding the repair of the rear defroster grid. It is very rare for the grid to actually be working and it seems that the ones that do work are in a hot, dry environment where it is not needed anyway. go figure.

Some folks simply don't care if it works or not and would rather there were a way to completely scrape off the grid. However, it seems that it cannot be scraped off completely. I guess some of it is embedded in the glass itself.

The repair kits that are sold seem to be geared toward grids with a single inch long brake in the grid, rather than a grid that is deteriorating in multiple areas.

I want my rear defroster to work (I live in Minnesota!). I have the window out of the bus now for a painting project. I have yet to read a success story with regard to repairing a deteriorating defroster grid, but maybe some of the threads just hadn't been followed up on.

-Has anyone successfully repaired a broken or deteriorated defroster grid?

-Does anyone know the specific layers of materials that make up the grid (copper wire/glass/silver paint/ etc)?

Lets hear from those who have tried to scrape off the grid with a razor. How far down did you get? is it just the wire that is left when you've scraped it smooth to the window? is it easier to see breaks in the copper once it is scraped? any pics?

I am wondering if it is possible to "rebuild" the grid: tearing it down as far as I can go with it and then building it back up with better materials that preferably will not deteriorate in a less than arid environment. I have good power going to the grid, so I know that the issue with my defroster is the grid itself.

thanks guys! Lets solve this issue once and for all! :-)

Thu Sep 09, 2010 8:58 pm

Here in the pacific NW it would be great to get my defroster working before winter. My grid is completly toast.
-
MD

Thu Sep 09, 2010 9:17 pm

Hiya berd,

Yes, I have successfully repaired a rear window defroster grid. But one does need to know that............

The grid was fairly new (a replacement rear window for a Bug) and had but a single break. In this particular situation the repair kit (actually just a miniature bottle of paint with a high metallic content) did work. Don't even begin to nurture the possibility that this paint will fix up and older grid with many breaks.

I do not know the composition of the OEM grid material save to say that it had a high metallic content and was baked on the glass.

I do not believe that there is any wire per se in these grids. To my knowledge they are stenciled on and baked in place. Finding breaks in these older grids can be pretty frustrating even with the help of measuring resistance. The lines can look reasonably solid but not have enough metallic content to conduct the juice.

I'm guessing that it is possible to rebuild the grid. It would take money, equipment, and knowledge. I don't have very much of any of those three. However, there are some companies (Frostfighter comes to mind) that have gone this route and sell kits to re-establish grids on windows.

Thu Sep 09, 2010 9:36 pm

best thread on this had a simple suggestion. Hook a 12v small light up to a wire to ground on one side and to a small piece of aluminum foil on the other. Slide the foil across the grid line. Every time the bulb goes out there is a break.

I would not expect a lot out of a 35 year old window. My Acura Legend grid was like new but after 15 years of use it heated about 1/3 as fast. I think the best solution if you want one that works is have a glass shop make you a new one and save the old window for a show or until you find a like new or NOS one.

Thu Sep 09, 2010 10:00 pm

^ That's a good method! I was curious so I just went out to check if mine's working and no luck. I get the power but the grid is screwed. I inspected it afterwards and I can see like three ~1" spots where it's missing. Oh, well... maybe I'll get around fixing it sometime.

Fri Sep 10, 2010 12:14 am

Alternative:

17
Glass,rear screen,heated,8/64-79
[211-845-501/HEAT][IN STOCK]

£59.21

Heated rear tailgate glass - Van or Microbus

from http://www.vwheritage.com/

Fri Sep 10, 2010 1:53 am

Just replace the grid with a new one.

http://www.frostfighter.com/prt2600.htm

Fri Sep 10, 2010 6:19 am

Bookwus wrote: Hiya berd,

Yes, I have successfully repaired a rear window defroster grid. But one does need to know that............

The grid was fairly new (a replacement rear window for a Bug) and had but a single break. In this particular situation the repair kit (actually just a miniature bottle of paint with a high metallic content) did work. Don't even begin to nurture the possibility that this paint will fix up and older grid with many breaks.

I do not know the composition of the OEM grid material save to say that it had a high metallic content and was baked on the glass.

I do not believe that there is any wire per se in these grids. To my knowledge they are stenciled on and baked in place. Finding breaks in these older grids can be pretty frustrating even with the help of measuring resistance. The lines can look reasonably solid but not have enough metallic content to conduct the juice.

I'm guessing that it is possible to rebuild the grid. It would take money, equipment, and knowledge. I don't have very much of any of those three. However, there are some companies (Frostfighter comes to mind) that have gone this route and sell kits to re-establish grids on windows.

Actually they are screen printed (not stenciled) with specific metallic inks. To have the correct reisstance, the dimension and ink thickness of each line is tightly controlled. At this point the ink is NOT conductive. It just contains metal.

The glass is printed flat, then draped over a mold and run through a lehr or oven. The heat fuses the inks into conductive lines at the same time it shapes the galss to the mold.

This annealing/baking/fusion process is why the lines leave marks in the glass.

Because of the curve of the glass, it is exceddingly difficult (not impossible) to reprint the glass. On those you can reprint....the glassgenerally does not survive a second trip through the oven.

Conductive inks have come light years. There are a very few conductive inks that are very low temperature for fusion. The issue is that they have less conductivity and heating ability and less life and are expensive for this process.

The frost fighter kits are nothing like factory. They are not only thicker and wider (not a bad issue)...they are simply copper inductuion grids with high perforamnce adhesive backing.

They should work fine, but will be easily scratched loose or moved if you are not careful. They will also tarnish.
Just bear in mind that they are not as permanent as factory. If you have lots of condensation or clean your rear windows often...it will sooner or later undermine the adhesive. But for $49...they are a bargain.

There are other ways to make grids...other inks and other chemicals. Most are very tedious but some have good results. Ray

Fri Sep 10, 2010 6:46 am

Ray explained this pretty well. The conductive ink is a paste made of silver and ceramic frit. The silver conducts the electricity and the ceramic bonds the silver to the glass when baked. The brown / orange lines are actually silver when the glass is new. The silver oxidizes and turns the brown / orange color. The reason the heater grid stops working is because the silver is scraped, worn, or oxidized away.

Fri Sep 10, 2010 7:38 am

exchanged e-mails with VW Heritage. Their windows are made in Finland.

Fri Sep 10, 2010 10:58 am

waltervee wrote: Just replace the grid with a new one.

http://www.frostfighter.com/prt2600.htm

I came across this site a while back and plan to purchase one soon. I've even posted links to them as well, but don't know if anyone's tried them. I'll let y'all know how it works out. Peace!

Fri Sep 10, 2010 11:12 am

Althea78 wrote: Ray explained this pretty well. The conductive ink is a paste made of silver and ceramic frit. The silver conducts the electricity and the ceramic bonds the silver to the glass when baked. The brown / orange lines are actually silver when the glass is new. The silver oxidizes and turns the brown / orange color. The reason the heater grid stops working is because the silver is scraped, worn, or oxidized away.

Thank you! :D I have actually printed some of them. The screen printing industry (all of it) is my business. I train screen printers of all types (solar, electronic, industrial, textile and graphics).

Most modern defroster inks are not actually "frit" anymore (your explaination of Frit was spot on). Frit requires too high of a fusion point. Most are simply low melt point metallics.

The very original first defrosters were made exactly as you pointed out...with the ceramic giving the gold orange color. Even as early as the late 70's...this process went away. Metallic inks (not always silver but alloys of several metals) were printed first and then overprinted with a protective glaze and then fired.
The reason for this is that in the original method...the frit interferes in the fusion and conductance of the metal. It required more pure and therefore more expensive conductive metals in order to have proper resistance.

Also with the original frit partially bonded into the conductive metal...it means that the metal is not fully sealed from moisture. This is why the silver can oxidize away leaving only the orange frit layer.

Newer defroster grids are fully sealed metal layers. Ray

Fri Sep 10, 2010 1:40 pm

1977_L63H_P27 wrote: waltervee wrote: Just replace the grid with a new one.

http://www.frostfighter.com/prt2600.htm

I came across this site a while back and plan to purchase one soon. I've even posted links to them as well, but don't know if anyone's tried them. I'll let y'all know how it works out. Peace!

I've been curious about this as well - anyone out there tried the above frostfighter kit?

Mon Sep 13, 2010 7:04 pm

THanks for all the info.

I had seen the frostfighter links before, but I would be curious (as the others are) to see how it performs, and how the install goes.

A new window with a defroster grid would be awesome. but checking the link above, it would be $120.00 from VW heritage before factoring in the shipping cost from overseas. I could search for a distributor around here. But I wonder now how the grids are made on these replicas.

I also want to tint this window, which will add another layer of complexity to the process and the functionality, I assume.

Mon Sep 13, 2010 8:30 pm

Ray - do you know anyone who would make custom bus rear windows for a group buy? Ours is green Duro glass similar to the PPG green tint on new bay front windows. Most will be clear. But I believe they are completely flat and probably tempered.

Tue Sep 14, 2010 6:57 am

I can look into it. It might take a little while. Anymore the defroster grid is the easy part. many of them are no longer screen printed...but actually ink-jet printed and then baked. So set up is much cheaper. Its really all about getting the requisite glass made and then getting into a production line. I'll see who I know...who knows who can do it. Ray

Thu Oct 07, 2010 10:48 am

VEC-2 wrote: All of my OG silver traces were damaged but the end sections are in good shape with power from the dash switch. After scraping off the original traces with a razor blade - I installed new traces from Frost Fighter directly over what was left. I did not like Frost Fighter's trace end attachment method so I used their conductive epoxy to attach the trace ends to the OG VW silver end sections. See my pics in the Gallery. Gets nice and warm. The kit did come with a nice switch and a timed relay for auto turn off. Have not made my mind up yet on whether or not to use them or keep the OEM "turn on and stays on" switch.

I found this in another thread on the subject. I've just ordered the #2906 Stick Kit from Frost Fighter and will post up after I've installed it. I may buy the repair epoxy and attach mine to the original VW ends, as mine are still in great shape. Peace!

Thu Oct 07, 2010 2:33 pm

of course mine works perfect since I dont drive it in the winter. oh the irony.

Thu Oct 28, 2010 10:56 am

1977_L63H_P27 wrote: VEC-2 wrote: All of my OG silver traces were damaged but the end sections are in good shape with power from the dash switch. After scraping off the original traces with a razor blade - I installed new traces from Frost Fighter directly over what was left. I did not like Frost Fighter's trace end attachment method so I used their conductive epoxy to attach the trace ends to the OG VW silver end sections. See my pics in the Gallery. Gets nice and warm. The kit did come with a nice switch and a timed relay for auto turn off. Have not made my mind up yet on whether or not to use them or keep the OEM "turn on and stays on" switch.

I found this in another thread on the subject. I've just ordered the #2906 Stick Kit from Frost Fighter and will post up after I've installed it. I may buy the repair epoxy and attach mine to the original VW ends, as mine are still in great shape. Peace!

So, I bought the kit :P. I, too, didn't like the way the ends were in the kit. I also didn't want to pay $30 for the epoxy they sell. I cleaned my window up real good, installed the grid line by line (to match my original lines) and used the Permatex kit to connect the ends to my original. I let the ends cure over night and tested the whole thing with a multi-meter. I was getting great readings. The final step in the Frost Fighter kit is to power it up for 15 minutes and let the glue set. I didn't have the window installed, so I brought a battery in to the kitchen where I was working. I hooked it up and laid my hand on the bottom 5 or 6 lines...and it wasn't getting warm. i waited 5 more seconds then decided to touch the top. I got a pretty good burn and, as I pulled off the power wire, glass exploded all around me with little bits of it stuck in my hands and arms. The instructions clearly states not to modify, but I thought I knew better, lol! I may order another but, I'll install it according to directions :). Peace!

Thu Oct 28, 2010 2:32 pm

1977_L63H_P27 wrote: 1977_L63H_P27 wrote: VEC-2 wrote: All of my OG silver traces were damaged but the end sections are in good shape with power from the dash switch. After scraping off the original traces with a razor blade - I installed new traces from Frost Fighter directly over what was left. I did not like Frost Fighter's trace end attachment method so I used their conductive epoxy to attach the trace ends to the OG VW silver end sections. See my pics in the Gallery. Gets nice and warm. The kit did come with a nice switch and a timed relay for auto turn off. Have not made my mind up yet on whether or not to use them or keep the OEM "turn on and stays on" switch.

I found this in another thread on the subject. I've just ordered the #2906 Stick Kit from Frost Fighter and will post up after I've installed it. I may buy the repair epoxy and attach mine to the original VW ends, as mine are still in great shape. Peace!

So, I bought the kit :P. I, too, didn't like the way the ends were in the kit. I also didn't want to pay $30 for the epoxy they sell. I cleaned my window up real good, installed the grid line by line (to match my original lines) and used the Permatex kit to connect the ends to my original. I let the ends cure over night and tested the whole thing with a multi-meter. I was getting great readings. The final step in the Frost Fighter kit is to power it up for 15 minutes and let the glue set. I didn't have the window installed, so I brought a battery in to the kitchen where I was working. I hooked it up and laid my hand on the bottom 5 or 6 lines...and it wasn't getting warm. i waited 5 more seconds then decided to touch the top. I got a pretty good burn and, as I pulled off the power wire, glass exploded all around me with little bits of it stuck in my hands and arms. The instructions clearly states not to modify, but I thought I knew better, lol! I may order another but, I'll install it according to directions :). Peace!

So you hooked the power directly to the grid...or through the switch?

It sounds like either the grid you made did not have enough resistance (what did your grids resistance read)...or there should have been a dropping resistor in the switch unit. Also.....at $30 for epoxy...it was probably conductive epoxy...which is worth $30...and adds to the resistance. Ray