Rear heated window -- need details on the electrical connection location...

[Jim Williams]

I have a '73 coupe I purchased about 3 years ago which has been waiting on a rebuilt engine. I am nearing completion of the engine, and a few other modifications to the car to get it ready for the street. In doing some rewiring for the 3.1 liter engine going into the car, I have noticed that the wires that should come from the heated rear window are nowhere to be found. The rear relay panel is equipped with the dual rear window heating relay, but no wires to connect to the window. I have peeled back the rear window gasket from the inside of the car, and found what appear to be connections to the deposited grid on the left side of the window. But, there is no apparent way to hook connectors to them under the gasket from the side facing the inside of the car. If there is a male spade lug or similar, it must face the outside of the car, and must be hidden under the other side of the window gasket.

Can anyone familiar with where the wires to the window actually connect, post a photo or a sketch, or furnish a reference of a drawing that shows where I should be looking? I would like to re-connect the window heating elements if possible before winter.

BTW, I have checked the connections and found that I have electrical continuity between the elements, approx 22 ohms.

Any suggestions would be appreciated.

[ossiblue]

Jim,

The wires from the relay typically have to be pushed through a hole you punch in the seal (on the inside of the car) to attach to the connectors on the window, then the wire is tucked under the seal when the window is installed to hide it. If this sounds like a PITA, it can be and that's why many of our cars do not have working defoggers, especially if the seals have been replaced by other than an owner or a concerned Porsche shop. You're lucky--you still have the connectors on your window. Many of us have had them broken off by careless installers. Sorry I don't have a better picture.

[1982911SCTarga]

Jim, I don't know how this may translate to your '73, but here's a look at the diagram I drew when I replaced my '82 Targa's rear window and thus re-did the defroster connections. My rear window defroster is a two-stage system (and yes, it properly works).

The following is as if you were viewing the car from the rear:

-- There are six spade connections (some single and some dual) around the perimeter of the rear window, with three on each side.

-- On the driver's side, the outermost connection (which could be considered as being located closest to the driver) takes a black jumper wire that also connects to the third spade set (which would be closest to the middle of the window). Opposite this dual spade connection goes a red/black wire.

-- On the passenger side, the situation is similar. A black jumper wire goes from the most-distant spade connection to the closest spade connection (of the three on the right side). Opposite the dual-spade connection in the nearest set goes a brown wire (brown is almost -- if not always -- the ground on our cars).

-- Staying with the passenger set of three spade connections, the middle connection point of the three is for another brown wire (a ground again).

-- On the driver's side set of three spade connections, the middle of the three takes a red/white wire.

-- The order of hole drilling for the wires through the seal and then through the harness body grommet is (from left to right) red/white, red/black, brown and brown.

-- These four wires pass through the body and into the engine compartment. The brown wires ground to the body around the fuse panel mount/CDI box area.

-- The red/black and red/white wires go into a two-prong connector that attaches them to like colored wires under the fuse panel.

Hope this helps.

By the way, I'm almost certain an enterprising DIY'er could solder attach new spade connections if some were previously broken off.

The wires get tucked into their own seal flange around the window once the window and seal is roped into the body.

Brian

[robmog]

jim,
here are a few pictures to add to brians comments
from my 1972.
three wires come from engine compartment on drivers side and enter the seal.
the red/black and red/white wires go to the spade connectors on the Left
heres a closeup to show the wire in the channel

the brown wire runs along the bottom edge to the Right side
there is a series jumper wire also on the right to complete the circuit
good luck,
bob
oops, the last picture is upside down

[Jim Williams]

L.J.,

Thanks for the info and the photo. From the photo, it looks like the spade lug is pointed toward the inside of the car interior. I am going to attach a photo if I can can get a decent one. The small metal bracket (for lack of a better term) attached to the metalized bonding on the inside of the window looks as though, if there is a spade lug as a part of the attachment, it is pointed toward the outside edge of the window, not the inside. I can't see a spade lug on the metal bracket. If a spade lug is there, it goes through the gasket material and is not visible.



(The nuts are there to hold the gasket back for the photo, if that's not obvious...)

Does anyone know for sure which way the spade lug points? If it's toward the outside edge of the glass, I'm going to have a heck of a time accessing it with the glass in place!

There are three of these small brackets, and none of them appear to have anything broken off, from what I can tell.

Brian,

It sounds as if your Targa rear window wiring is a good bit more complex than mine. I only have wires on the driver's side.

Robmog,

I suspect your '72 is pretty much the same as the '73. And thanks for the photos. What I am still having trouble visualizing is which direction the spade lugs point, towards the inside of the car or towards the outer edge of the window. Do you have the actual window? And if so, could you make a photo of the spade lug? This would answer a lot of my questions.......

[robmog]

jim,
i cant imagine rewiring w/o removal.
i'll post pictures of the window tomorrow.
bob

[1982911SCTarga]

Jim, there may be a difference between coupe and targa rear defroster wiring, or you're not seeing all of your connections.

On a targa rear window, all of the spade connectors are along the outside edge of the window -- a "V" is cut to allow the wire to exit immediately from the window flange and run in its own wiring groove/flange in the seal.

There's no way you can rewire/repair your rear window defroster wiring in situ. Take your rear window out, work out the appropriate wiring connections and use a new seal to replace.

Photos of my experience here.

Brian

[Jim Williams]

I am beginning to come to grips with the fact that I'm not going to be able to accomplish much in the way of re-attaching the connections to the window from the heater relay, without removing the window.

Anyway, here is some follow-up information on the heated rear window... In spite of the fact that a dual element heated rear window has been available as a factory option since the early cars (at least a '72), the first factory wiring diagram that acknowledges this I have found is in the wiring diagrams for the '75. This diagram shows three electrically separate elements interconnected to make two elements by means of short jumper connections between two of the separate elements. This would represent Brian's rear window.



However, this is not the configuration of elements in my '73. It is clear from looking at the window from the outside of the '73 that the actual heater elements in the '73 are not configured as the later ones, although the same dual position relay may be used from at least '72 up though at least '81.

On the '73, on the right side of the window, all the individual "wires" that run from side to side (19 of them) are connected together on that side with a long deposited strip. I can find no evidence of a ground wire connected to this long wide deposited strip, and can in fact find no reason to have one. I believe the only ground connection to be on the left side of the window at the bottom-most set of deposited wires, and the other connections (red-white and re-black) made at the other two element sets.

On the left side there are two breaks in the long wide strip running from top to bottom, creating 3 elements with a common connection on the right side via the long wide top to bottom strip.

Here is the above diagram modified as to how I think the '73 heater elements are wired.



The black line connecting the three elements is part of the deposited conductor on the window and not jumper connections inside the window gasket.

Comments?

[robmog]

jim,
here's a closeup of the spade connector, you can see this would be inside the gasket.
left side (upside down inside surface)
red/black goes to spade at top
red/white to middle
right side same orientation
brown to spade at top
you were spot on about the jumpers which are visible in the pictures.
good luck
bob

[Jim Williams]

Bob,

Thanks for the photos. The one of the spade connector itself answers most of the unknowns about my window. I had not figured out from my inspection or from the photo from ossiblue how the spade itself was oriented.

There still exists another possibility on wiring of the window on my '73 that the use of these jumpers brings to mind. My window could have a jumper on the driver side, and one ground connection on the passenger side. I have not thoroughly peeled back the gasket on the passenger side to look for a connection there, and this would actually make more sense than the assumption I made in my modified circuit diagram above.

(time out to double-check the passenger side of the window)........

News Flash! Yep, you might have already guessed. I found 2 spade lug connections. One near the top of the window, and one near the bottom. I don't know why two were felt to be needed, unless they were dictated by the current limitations of the deposited strip. So I'm making one last correction to the wiring diagram, just to clear up the situation as I now see it. The black thin line connecting the bottom of the elements is the connection deposited on the window. I'm assuming that when I get ready to pull the window and re-do the connections, two ground connections here would be on the safe side.

Thanks to all who helped me out with this.

[RX911]

jIM,
I'm not sure this will help, but I have a 1980 sc that I am changing the rear glass seal on. It is in a condition that you can easly peel back the rubber on the inside or out to look at the wires. The old seal is trash but still in the car. The plus for you is that I live across the street.

tom f

[Jim Williams]

Hi Tom,

This would be great to see how the wiring is routed in the seal. I can't find your email or telephone number, or figure out how to send you a PM for that matter on the new Pelican Format. My email is jwms911 at comcast.net.

[MZ3 SBC]

can anyone post a clear drawing or picture of the following for a late 70s early 80s dual circuit rear defroster spade connection.


I have a red and black and a red and white power. I understand they connect on the driver side. red black to the top and red white to the middle. how do I jump the lower.


I have two browns...one goes tot he top space on passenger side, and one to the middle. How do I jump between them.


thanks...I am close to reinstalling the glass.....

[Jim Williams]

Go back to the above posts with the wiring diagrams starting with #8. Where are the deposited connections on the window - both sides? And which is which?

In other words, which post looks like your window?

Not quite sure what you mean by "jump the bottom".....

[MZ3 SBC]

My window looks the same as the one in the #8 post.

I keep rereading this ...its like watching abbot and Costello perform whose on first!

By "jump to the bottom" I am referring to the black jumper wires.

Originally Posted by 1982911SCTarga

Jim, I don't know how this may translate to your '73, but here's a look at the diagram I drew when I replaced my '82 Targa's rear window and thus re-did the defroster connections. My rear window defroster is a two-stage system (and yes, it properly works).

The following is as if you were viewing the car from the rear:

-- There are six spade connections (some single and some dual) around the perimeter of the rear window, with three on each side.

-- On the driver's side, the outermost connection (which could be considered as being located closest to the driver) takes a black jumper wire that also connects to the third spade set (which would be closest to the middle of the window). Opposite this dual spade connection goes a red/black wire.

-- On the passenger side, the situation is similar. A black jumper wire goes from the most-distant spade connection to the closest spade connection (of the three on the right side). Opposite the dual-spade connection in the nearest set goes a brown wire (brown is almost -- if not always -- the ground on our cars).

-- Staying with the passenger set of three spade connections, the middle connection point of the three is for another brown wire (a ground again).

-- On the driver's side set of three spade connections, the middle of the three takes a red/white wire.

-- The order of hole drilling for the wires through the seal and then through the harness body grommet is (from left to right) red/white, red/black, brown and brown.

-- These four wires pass through the body and into the engine compartment. The brown wires ground to the body around the fuse panel mount/CDI box area.

-- The red/black and red/white wires go into a two-prong connector that attaches them to like colored wires under the fuse panel.

Hope this helps.

By the way, I'm almost certain an enterprising DIY'er could solder attach new spade connections if some were previously broken off.

The wires get tucked into their own seal flange around the window once the window and seal is roped into the body.

Brian

[MZ3 SBC]

Picture of defroster wires

[MZ3 SBC]

This job is tougher than it looks...

[Sigurd]

I decided I did not need the heat, to much work to route the wires. I now have a switch for the fog lights

[MZ3 SBC]

My first attempt was a total failure.

- made the holes in the wrong part of the seal...ran the wires in the wrong channel

gotta buy a new seal and try again. Having been through it once now...all the member posts make sense to me.

[Dpmulvan]

Let me know if you need some help I happen to have my back window out right now with the electrical connections still intact.