Rear window defrost

[Guest Kickerz]

My rear window defrost in my 99' SUS seems to get warm at best and takes awhile to get there. Any ideas to why it takes so long to get warm and why it doesn't get hot enough?

 

Thanx in advance

[Guest OutbackKY]

Can you explain in a little more detail? Can it clear a simple fog? How about snow? Ice?

 

Bryan

[Guest Kickerz]

It does clear fog or condensation nicely but IMHO not fast enough in comparision of past vehicles that I've had with RWD. When it comes to colder temps and ice formed on the back window it will take an honest 20minutes before a thin layer of ice is melted to where the driver can see clearly through the rear view mirrow.

[Guest OutbackKY]

Not trying to be a smartass (honest!), but have you ever considered using an ice scraper when there's ice on the windows? My guess is the defogger/defroster on the window was not designed to thaw out ice. 10 seconds of scraping ice goes much faster than 20 minutes of aggravation while looking into the rear-view mirror.

 

Bryan

[Guest SmashPDX]

FWIW the rear window defrost on my 95 isn't particuarly impressive. It won't clear much if there's buildup of anything (you know, like a coating of mist) on the outside. Pretty much need the wipers and need to heat up the inside of the car with the blower to get that stuff off.

 

I think the 95-99 setups are pretty much identical on this.

[Guest Torch n Hammer auto repair]

Did you check the fuse. Perhaps it isn't seated well or the amperage is wrong. It does sound like 20 min is too long. My OB wagon clears ice and snow pretty quick. If I keep the RWD on snow or ice will not accumulate while driving it will melt (15 to 20 degrees, moderate snowfall). On a good thick frost the RWD burns through the frost so the "wires" are clear in about 3 to 4 minutes.

 

Bryan,

Why scrape? That whole clear vision thing is way overrated! :-)

Greg

[Guest SmashPDX]

Torch,

 

What year is your OB?

[Guest Torch n Hammer auto repair]

Russ,

I should have been more clear. My wife HAS a 96 OB and I get stuck with the 91 Legacy Wagon. Both 2.2, 5 speed AWD. So understand when I say "I have an OB" that means I wash it, wax it, change the oil in it, clean the interior, put tires on it and drive it when she lets me!

Greg

 

BTW the 91 Legacy RWD cleans off pretty quick too.

[Guest SmashPDX]

Heh...

 

Guess I'll go check the fuses on my '95. Any idea which specific one it is?

[Guest Torch n Hammer auto repair]

Russ,

It is fuse #7 under the dash on the drivers side. 20 amp.

Greg

[Guest mrtoyou7747]

Cleanliness of the rear window does have an effect on the efficiency of the RWD. Thing's don't stick well to clean surfaces.

 

The heat produced by the RWD is proportional to the square of the voltage applied to the heater grid. So small decreases in the voltage at the RWD terminals will have a significant effect on the "heating" of the window. In the winter when you first start the car (recharge battery) run with the lights and heater blower "on" you will have a lower voltage at the RWD as the battery is being recharged. Todays cars with all the electronics and accessories running will draw a lot of current

[Guest canajun2eh]

I had that "slow defrost" problem with my 92 Legacy wagon.

 

It turned out that I had *3* bad electrical connections in the defroster circuit. One was inside the tailgate (bad ground), and two were in the wiring run from the rear to the front. There was a fair bit of corrosion in two of the connectors inside the passenger compartment (right side).

 

When I fixed these bad connections by making permanent soldered connections instead of the plugs, the functioning of that defroster improved dramatically. The defroster will now melt 1/4" ice within 5 minutes to the point where the rear wiper will clear it off easily.

[Guest Sam]

I agree that you ought to clean the connections on the rear window. Be carefull as the metal tabs can brake off easily.

[Guest SmashPDX]

Hmm guess I'm going to be doing some defroster 'tune up.'

[Guest NV Zeno]

Hmmm...me too.

[Guest Bagheera85]

There's kits you can buy that can find the lines that have a break in them.. sometimes, if you look closely, you can actually see them yerself.

[Guest Kickerz]

Thanx for all the replies! I guess I was looking for an easy fix but unfortunately I think I'll have to go through and see what type of amperage I have at the fuse box and compare that to the connections in the back of the car. If the amperage drop is significant I probably have the same problem as Gerry. I'll keep the board posted as repairs are under way.

 

Oh, and yes scraping does help alot Bryan but if you have the RWD option why scrap just hit the button. Like Gerry's OB, the ice should melt off in no more than 5 minutes. Me just being lazy I guess.....

[Guest SmashPDX]

I stuck this thread to the top because it's on its way to the archives, if you want to add stuff then do so now, going, going...

 

And oh, can anyone tell me where those contact plugs are on a 92 sedan? Haven't exactly ripped things apart at the rear window just yet, but in spite of having 5 volts at the centerpoint of each element 'line', there is very little heat being generated.

[Guest mrtoyou7747]

5 volts is low to me means you have some significant series resistance in the contacts or the wiring.

 

Remember P=Vsquared/R so 5 volts wil give you 25/36 of the power (=heat)

[Guest SmashPDX]

Ok, so where are the contacts?

[Guest keenr]

"My wife HAS a 96 OB..." "I wash it, wax it, change the oil in it, clean the interior, put tires on it and drive it when she lets me!" I know THAT story! At my house it went, "I need a mini van." Got one. Now I hear, "It's too big and too hard to park. I'll just take YOUR car."

[Guest mrtoyou7747]

The contacts are the metal "tabs" which are bonded to the metallization on the window (where the traces start) to which the wires are attached.

 

Make sure that they are tight and not corroded from water etc.

 

Be carefull they are only "glued" on. If you break them off you can replair them with some special goup you can buy at the auto parts place

[Guest SmashPDX]

Hm. Well, since I seem to be talking something different I guess I'll have to just pry open the panel behind the back seat.

 

On the 92 Legacy sedan these contacts aren't visible. Yeah, they're back there, somewhere, but since they have to be there and they can't be seen they must be under the panel the high stop light and speakers are sitting in/on. Will figure out how to pry it up and see, and then I'll tell you guys and we can archive this thread for posterity

[Guest SmashPDX]

Ok, I went after the defroster contacts. Didn't get to 'em but I think I know where they are. On our 92 sedan the wires disappear behind some internal body panels and the contacts are probably there. Trouble is, those body panels are wedged in place by the back seat, which doesn't fold down. I'm sure there's a proper way to get those panels off but I don't know what it is, and from what I gather from the Mrs. the defroster works great so long as you're moving (or the engine is running, I suppose).

 

So I'm done a-chasin.' Thread is heading to the archives. Going, going...

[Guest Legacy777]

Getting the back seat off is pretty easy if you wanted to get it off to do some more looking.

 

There are two bolts that hold the bottom cushion on. Then you have to lift the front part of the bottom cushion up, so the back side drops down and unhooks from the top portion. Slide it out, take out the three bolts that hold the top cushion in, and then lift the top cushion upwards and unhook it from the car.