Rear Defrost Improvement possible? 1985 300TD W123
 

Anyone Know of a way to make the rear defrost more effective? It seems to work but very slownly and It cycles off before its totally defrosted. Are the little contacts on the window solderable? Do you need to replace the rear window if you want to replace the defrost heating strips on the window? Could that be the problem?
Thanks all

how cold is it? I think the rear defroster switch is on a timer, so if you have a lot of humidity in the car it'll be hard to defog all the way. if it's FROST on the outside of the window, and you are driving, it's REALLY hard to let the defroster handle frost. best to REMOVE The frost from the outside, and let the defogger system keep it free.

Well, now its not freezing yet but the two years Ive had the car its been very cold up here in the winter compared with most of you down south. usually a thick frost or freezing rain on the window.

t just seems weak on one or two particular strips. Most modern cars I drive can handle a good layer of ice or frost within 10 or 15 minutes of driving.

Permatex sells some copper defroster grid repair paint.

But, on my window that has the grid exposed on the inside the Copper grid lines appear solid but are actually corroded. The corroded spots in the pic are dark brown and the break the electrical connection.
(Someone replaced my Rear Window from one that came from a Junk Yard where it must have been exposed to the elements.)


Someone on our forum posted the below site:
Window defroster defogger repair grids
http://www.frostfighter.com/

1982 300 SD
 

My guess is that your MB is similar to mine. If I am correct, the comment regarding the repair of the wires already present is accurate. We live in Buffalo, NY and experience harsh winter weather conditions. My MB rear defrost is faster than the Honda, or any of our Chrysler or Ford products. My guess is that repair of the grid is more painful than replacement, but I suspect a good auto glass shop has the proper equipment / skill set to make you smile.

I'm no electrical engineer, but I wonder if a person couldn't use a transformer to bump the voltage of that circuit up to, say 24v? Of course, it wouldn't help if the grid is in sad shape to begin with.

Nope, transformers only work with AC current. Cars use DC.

ninja edit:

DC-to-DC converter - Wikipedia, the free encyclopedia


^ New to me, never knew.

My 560 is sub-par also. But my wires are within the lamination of the glass. Not on the inside or out. The wires are so small they are hard to see. They also take a long time to defog or melt ice. My Mark VIII could toast a bagel if it wanted to. Both had a max time limit before automatic shut-off. I think around 10 minutes.

I replaced the rear window on my 126 with a brand new replacement part - new grid, in other words. It's still quite pathetic and takes a long time to melt ice on a cold day. In Winterpeg on a cold -30C night I think you would see it take forever to melt ice.

Princess Auto and other "cheapo" parts places used to sell little warm air heaters that sit on the parcel shelf and blow hot air onto the back window - power it off the cigar lighter outlet. Just a thought....

I'll be damned, never knew such as think existed.. I stand corrected

Still, going to 24V may make the element turn into a busted fuse. I'm thinkin' extension cord... blow dryer.

The hot extension cord is exactly the effect this relies on. My gut says that if it doesn't work, there must be something to be repaired, but the coldest day I've ever had to deal with was 10F. That window exposed to sub zero is a hell of a heat sink. If the circuit doesn't get hot enough to melt ice, it can't get hot enough to melt the element! Maybe these northern types need a dual range element - a regular duty defrost and a sub zero mode. I'm just speculating, normal works excellent for me.

does any one know what resistance the window wires are supposed to be? My thought is they have gone up in resistance to the point that they will not pass enough current to heat up. Prolly due to age. I get good voltage to the wires but no current at all.
I may try scraping the old stuff off and trying the Frostfighter....

As I'm reading this, something is telling me this system is only a defogger, not defroster. Maybe someone could confirm this?

Mine works on the top 4 rows, but not on the rows below that, always room for improvement.