ThePointman

Anyone have a used one to sell and know where the derost relay is located on an 85 Carrera?

Dan Cobb

If you've ever had the rear window out and seen the rat-nest of wires associated with the rear defroster, you'd probably just yank it all out to save the weight and frustration of putting it back together.
Mine was out last winter and is currently non-operational due to an improper install by the window guy.
I'm looking for a qualified place to R&R the rear window again to replace the crappy gasket that I purchased and to hopefully correct the defrost wiring. I've been hesitant to open it up again due to the high cost of replacement glass and the fear that the problem is actually on the window rather than in the wiring.
Anyway, according to my Bentley Manual, the relay you seek is located in the engine compartment on the drivers' side. It appear to be the larger of the 2 relays, located on the side closest to the firewall.
I hope your repair is this simple.
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ThePointman

Considering the relay is $117 USD I hope it is the problem. I will do some electrical meter sluthing before purchase.

Dan Cobb

Check this eBay auction

No affiliation, etc. just happened to see it.
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dependencies

why then, does the de-frost switch on the dash, apparently have two settings ie,
push/pull
twist on/off

Dan Cobb

Interesting. I have never attempted to rotate mine. This is now on my 'to try' list.
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dependencies

Either the rear screen has two stages to choose from in de-frost, or
front screen works too.

Or mirrors de-frost, either way, none of mine do at the moment,
allthought the rear used to.

theiceman

apparently the rear has a 2 stage defrost, low and high heat .

dependencies

do you know, which way the switch is 'pointed' and how the screen defrosts






sort of thing

Dan Cobb

I tried today and it seems that my mirrors get warm to the touch when I rotate the **** AND when I pull it out.
I will attempt this again with a bit more control on the variables soon, as I am still unsure that I have a clue what I am trying to accomplish with either position.
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dependencies

Well mine being an import from Germany, it came complete with books in native,
which sadly I do'nt understand, I've yet to have the various controls properly explained, and perhaps someone here, uses them routinely.

Noel

Mine doesn't rotate.

One thing to try with the relay is to have an assistant pull the defrost switch with the ignition on. You should be able to hear the relay click at each stage. It may be tough to hear if you have an SC since the CD box will be screaming. The real way to find out is to measure the voltage coming out of the other side of the relay.

I think I have the same problem as Dan. When my glass was out to re-paint the car in the 90s, I think some wires got cut, as I can measure no voltage in the glass, but can coming out of the relay.

Good luck.

r911

I have a tidbit on this - my 1973.5 car has 2 ground wires and 2 hot wires going to the rear defroster grid. Not sure why that is so, but that's what I saw when the glass was out recently.

Dan Cobb

Very true Randy. I too cannot explain the reasoning behind this other than the possibility that creating 2 separate circuits (in the glass anyway) has something to do with the amount of resistance created by the thin 'grid' of 'wire'. This system operates by the resistance of this grid generating heat when a voltage and a current is applied. I'm guessing it had to do with reliability (ha ha)

Anyway, today i rotated the **** CW about 15-20°. It stopped as if it was designed to, so I didn't twist it any more than that. My mirrors definitely got warm. I will try pulling it next time to see the results.
I'm also going to crack open the owners' manual (What fun is that!?)
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r911

Good luck with your new-fangled car with -- can hardly believe it -- heated mirrors!