Can The Rear Defogger Grid Wires Be Re-soldered back on (123)? - Page 2 - PeachParts Mercedes-Benz Forum

Diesel911 · #16 12-09-2008, 05:21 PM

Quote:

Originally Posted by DeliveryValve

Can you post pictures of these vents and copper strips that your talking about?

BTW- I think you mentioned this before when you were rebuilding your rusty lower control arm.... Your car is not an original California car right? It seems to come from the east coast with all that rust!

I am just now getting back to look at this thread.
The is a pic from the manual showing where the Copper Strips were (there is 2; one on each side of the grid).

After scraping I found that I have a Holy car.

Diesel911 · #17 12-09-2008, 05:35 PM

update:
The acual grid is not damaged only the Copper strips are not hooked on.
Also my grid is on the inside surface of the window (you can fell it) and if it was scratched through could be repaired with that Copper liquid Repair (I have a vile of it).

I have already cleaned off the rust (batter than in the pic), used rust converter on the rust, I filled the holes with Epoxy Putty, sanded the putty down and primed and painted those areas.
After scraping as much of that gray window putty off with a plastic scraper I did use Paint Thinner to desolve and wipe off the rest.
As it turned out the really tedious part ended up being getting the Window Putty off of the old Windsield Rubber.
I again scraped with a plastic scraper and rubbed with a Brake Cleaner soaked rag until all of the residue was gone; took over 1 hour!

What is left is for me to let the paint on the car dry well and to Try to solder the Copper Strips back on.
Then it is on to the re-installation of the Rear Window.
I decided to try Henry 209 Elasomastic roof sealant. One of the uses is for sealing metal roofs so I figure it sould seal the window with no problems.
Yes, I am trying to get off cheap but I am doing this partly because it looks to me like it is going to take a lot of sealant to fill in what I want to fill in.

Diesel911 · #18 12-09-2008, 05:49 PM

Quote:

Originally Posted by samdon

I would assume, never having taken out the rear screen on a W123, that the copper strips running down each side of the glass are at least similar to the W115. You need to clean these strips well with Deoxit or the like so the solder will bond well: both those on the glass and the ones attached to the lead wires. Since these strips tuck up under the rubber gasket on the inside, I soldered them together then gently filed any stray solder lumps as smooth as possible with a finger nail file to get as good a mechanical seal as possible. Make sure all parts involved are hot enough to make the solder run rather than clump up. You'll see what I mean once you get into it. Use a pen torch instead of an iron if available. I can't see doing it properly without one really. You want the copper contacts right up against eachother rather than connected at intervals with a spot of solder. I tried generic ACE solder first and it did not work so well. I had some high silver content solder I used in a home speaker crossover project a while back and it did the trick nicely. partsexpress.com has what you need on the cheap.

Works like a charm now. A PO had replaced the rear glass at some point and just tucked the leads under the parcel shelf. No end to the shortcuts some folks will take to save a buck or three at the most.

Sam

Thanks
I have 2 mini tourches; someplace; have not used either for several years.

Diesel911 · #19 12-09-2008, 05:56 PM

Quote:

Originally Posted by fdanielson

Permatex makes a repair kit for rear window defoggers. There's an article about using it here- http://www.rd.com/familyhandyman/content/55830/

Thanks
I have one of those kits that is still good.
I also found I had 2 others but the liquid had evaporated from them.
I have used that kit on my gassers that had the scratched grid problem.

I found out when I bought the last one it is better to bring the part number and the maker Permatex along with you as Autozone an Kragen (Parts America) Counter Guys were not able to tell me if they had it or not from my description.
However, an independant auto part store had it.

Diesel911 · #20 12-10-2008, 12:13 PM

I found some papers under the seat that indicate the car might have come form the stae of MA. Or at least that is 1 of the places it has been.

patbob · #21 12-10-2008, 01:00 PM

Quote:

Originally Posted by Diesel911

The (-) and (+) copper strips (that I called wires) are there but were I guess left over from the origional window and not attached to the window.

These are normally bonded to the window. They are the mechanical strain relief and electricity conductor for between the wire and the delicate trace lines on the window surface.

Quote:

The replacement window that I think was a used one also has no copper strips or wires attached. However, the grid lines (exposed on the inner exterior of the window) all seem OK when I probed with my Ohm Meter.

One Member E-mailed me and said there is a conductive Epoxy. I will do an internet search for that as it should work.

You need to glue the conductive bars firmly to the window to serve as the mechanical strain relief. Is isn't important that what glue you use be conductive, just that it not come off. You might try the glue they sell in auto parts stores for gluing rear view mirrors back on.

Electrical supply places sell conductive paint pens that you should be able to use to bridge a connection between each trace and the conductor bars. They are sold for repairing circuit boards, so you'll probably need to find someplace that sells to the industry rather than a plain old Radio Shack. I'm sure they are also available elsewhere too. I'd check an auto parts store as its commonly touted in how-to's for repairing the things. You might have to gently scrape the surface of the traces to get a good connection with the conductive paint -- I wouldn't be at all suprised to find they are lightly insulated to prevent users from shorting the traces to the car body (amazing how dumb they can make idiots these days).

Caveat: I've never had occasion to have to try to repair one of these myself so what I say may be totally off base (but I suspect not or I'd have held my tounge). The only time I've had one fail, it was because the entire window got shattered -- they tend not to work too well in little tiny pieces, but fogging isn't a problem either (so I guess it's a double-edged sword

).

Remember to take pictures, I'm sure we could use a (another?) writeup on how to make such a repair.

rcounts · #22 12-10-2008, 07:15 PM

Quote:

Originally Posted by charmalu

The Coupe rear window is like the W126 with the wires laminated in the glass...

That's what I thought. Mine clears the fog from the glass in "streaks" - in other words, parts of it work whereas other parts of the grid don't work.

What kind of electrical connections are there between the wires? Are they exposed at the edge of the glass, or are the horizontal connections between the grid wires embedded in the glass too?

I'm trying to figure out if I can reapir it, or if I just have to live with it ('cause a new rear window for a coupe is E-X-P-E-N-S-I-V-E !)

Diesel911 · #23 12-10-2008, 09:06 PM

I was successful at soldering on the Copper strips!

I used but cannot recommend the Henry 209 Roof type sealant.
While I am sure it will do the job as far as the sealing goes it was extremely messy and got on me, clothing and other parts of the car that I did not intend to get sealant on.

But, the Window is back where it belongs. Just need to put back the side molding and read deck/carpet.