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Tue Oct 06, 2009 11:37 am

It's that time of the year - every morning my rear window is fogged up or getting frosted over.

I have a defroster switch and I see wires on the rear window (they've been painted over though), but the wire seems to be missing underneath the dashboard.

How is the wire routed to the back (haven't tore up my interior to find out yet)? Also, does the entire rear window need to be replaced if the wires are replaced and it doesn't work (was told by a local shop guy)?

Have any of you managed to repair your defroster?

Thanks,

- Joe

Tue Oct 06, 2009 11:42 am

I've never heard of someone on here with a working OG defroster. Someone asks every year, haha.

You'd have to replace the rotted wiring and scrape the original defroster off the rear window. You don't need to buy a new window, just remove the defrosting element. Then you can go buy generic kits and put it onto your rear window and hook it up. Basically you need to replace the whole system if you want it to work.

An ice scraper works just fine for me.

Tue Oct 06, 2009 11:45 am

cr@M wrote: I've never heard of someone on here with a working OG defroster. Someone asks every year, haha.

You'd have to replace the rotted wiring and scrape the original defroster off the rear window. You don't need to buy a new window, just remove the defrosting element. Then you can go buy generic kits and put it onto your rear window and hook it up. Basically you need to replace the whole system if you want it to work.

An ice scraper works just fine for me.

Damn it! I knew it wasn't going to be easy :lol:

Tue Oct 06, 2009 11:51 am

Joe, use an Ohm meter and check your existing grid. Then trace the wires back to the front. From that you should have an idea of the amount of work it will take to get it back close to OG. And a generic grid is always an option too. I'll just use a scraper myself.

Tue Oct 06, 2009 11:53 am

There's a reason why no one's works ;)

It's totally possible, i just don't see the point when the window is so easy to scrape. It is completely flat after all.

You don't even have the wiring hooked up to your switch? It would just follow the rest of the cables to the back I'd imagine.

Tue Oct 06, 2009 11:54 am

RocketRod wrote: Joe, use an Ohm meter and check your existing grid. Then trace the wires back to the front. From that you should have an idea of the amount of work it will take to get it back close to OG. And a generic grid is always an option too. I'll just use a scraper myself.

Been meaning to get a multimeter - thanks for the reminder.

Tue Oct 06, 2009 11:55 am

I don't mind using a scraper - I actually have a really cool one shaped like a cone that I found in my old 73 beetle I had a few years back. Works like a charm.

However, Ohio winters can be pretty brutal, and my wife and I are toying around with the idea of doing a road trip to see family during Christmas.

Tue Oct 06, 2009 11:59 am

Hang a curtain there and get used to it. ;)

They do sell repair kits for the window 'wires', and they work. (google that)

I just look at the side mirrors, but that's probably because I drove semi's for a bit of my life...

Tue Oct 06, 2009 12:10 pm

I don't know where I heard this or if it's true, but I've been told that rubbing a raw potato on the glass beforehand will help.

Aloha
tp

Tue Oct 06, 2009 12:19 pm

the wire, a heavy black one, goes from the switch to the windshield pillar near the passenger and through the overhead to the window in back. The ground is on the driver side. The switch gets its power from the fuse box.

You can buy an inexpensive kit made by locktite that has the copper colored paint in it to repair broken segments in the lines on the glass. Hook one side of a 12 V meter or 12 test probe light up to ground. Hook the positive probe or light tip up to a small piece of aluminum foil wrapped on it. Slide the aluminum foil gently across each line. When the light is lit or the volt meter shows voltage the line is good. When it stops you will see a small break normally. You put two pieces of tape together on the glass to make a small line and use the special loctite paint to paint the new line in the section that is damaged. That will solve most small breaks. If the whole windows is nothing but scratched then you can consider scraping it all off and using a kit. I would try the locktite paint first as usually it is just a few small breaks that cause the issue.

Wed Oct 07, 2009 6:41 pm

RIOMX - if you do get your rear defroster grid working, do your battery and charging system a huge favour - use the original defroster switch to turn on a relay (30 amp- use a good Bosch one) in the engine bay, and run the power for the defrost grid directly from the battery straight up to the rear window (through the relay).

That way, you avoid sending the 12 volts 18 feet forward to the fuse box, through the switch, and then 18 feet back to the rear window, which by then is much less than 12 volts. Instead, you end up with about a 3-4 foot run which delivers much more voltage directly to where you need it.

And also put a fusible link on the heavy duty power feed line as close as you can to the battery. Yes, its a bit of extra wiring, but well worth it.

Wed Oct 07, 2009 7:21 pm

Thanks for the extra wiring advice. I've never done wiring before, but this is good to know.

Since this seems like a project that can be really involved, I'll probably wait to do it until around the same time I do my second battery.

Wed Oct 07, 2009 7:41 pm

cr@M wrote: I've never heard of someone on here with a working OG defroster.

Mine works. :D

Wed Oct 07, 2009 7:51 pm

That's rare, all the ones around here have the silver plating eaten off from moisture in the air, little left but the brown etch primer on the glass.

Wed Oct 07, 2009 8:54 pm

dwill49965 wrote: That way, you avoid sending the 12 volts 18 feet forward to the fuse box, through the switch, and then 18 feet back to the rear window, which by then is much less than 12 volts.

If your wiring is totally shot or PO replaced with like 22awg crap with bunch of shoddy butt splices or something that extra work might be worth it, but if you've got decent 12-14awg or better on there, which is what the original wires look like at least, you won't lose much voltage at all if it's a clean run and that kinda gauge can certainly handle any current you throw at it... it's only going through an 8A fuse after all. I have a '72 resto project with OG defroster that I got working last week and am reading 12-12.2v at the rear terminal through the original wires. I can certainly live with that very minimal voltage drop. Keep in mind also that really cleaning your contacts can pick you up an extra half volt or more... I picked up about .3v after cleaning all mine. Not trying to be contrary.. just saying K.I.S.S. :)

http://www.itinerant-air-cooled.com/viewtopic.php?t=7199

Wed Oct 07, 2009 9:46 pm

If anyone has sucessfuly removed the grid from the hatch window I'd sure like to know how you did it. I've tried it on two busses, a '70 & '71, with the original Sakurat windows and it will not scrape off. It's imbeded in the glass and would take a grinder to grind it out. Don't know if busses ever came with just a clear glass without the defroster but have never seen one. Been tempted to have a glass company cut a new window. A defroster is totally useless here and I use the wire from the front for the third brake light.

Thu Oct 08, 2009 1:13 am

barefootwestie wrote: cr@M wrote: I've never heard of someone on here with a working OG defroster.

Mine works. :D

:shock:
My God....

Thu Oct 08, 2009 2:42 am

Is there a way to get what's left of the defroster off the glass?

Thu Oct 08, 2009 5:49 am

Tom,
Not only will the potato keep the glass clear, it will get rid of warts. After you rub it on the window, you rub it on the affected area. Then you have to bury it upside down in the yard (the potato, not the window) at dawn as you face East reciting the procedure for valve adjustment.

Thu Oct 08, 2009 10:19 pm

barefootwestie wrote: cr@M wrote: I've never heard of someone on here with a working OG defroster.

Mine works. :D
Mine [mostly] works! It doesn't quite clear the window but the grid lines do clear up most of the space 'tween them. Naturally, it is old and weakend and not up to snuff like my water-pumpers.

And alas, my Squareback only has one or two working lines :cry: