heated rear screen connections

[wilsonny]

Hello

i wonder if any kind person can offer advice or some pics of the correct connections to the heated rear windscreen behind the rear seat covers ? my heated screen has never worked, so i finally got around to take a look and can see someone at sometime has been attempting some fettling and not made a very good job. clearly one problem is that the passenger side window connection is missing, this i can fix, but the central connection has no feed to it and it appears that an additional cable may have been run underneath the window rubber to take this feed and try to supply power to the passenger side at some point. pics are attached...I'm looking to determine:

1. which coloured cables should be attached to each terminal
2. is the cable running around the window rubber supposed to be there
3. are there any other connections missing

i do have the wiring diagram, but I'd like to get the installation back to original rather than improvise what i think it should be.

many thanks for any pics or advice.

Regards

Andrew

 

[Graham-S]

Hi Andrew

Looks like Pic 1 (& Pic 3) should be attached to the solder mark at the bottom of the window

Pic 2 - Don't know!

If you put a multimeter on White/Red in Pic 2 it should end up through the wire in the window to where the brown wire should be attached to the glass in Pic 1

You can also test to see if you get 12V with Engine running and Heated window switch on at the White/Red and the Brown (Gnd) wire

Looking a Pic 2 again I think I can see another tab connector hanging off the Glass?? If so that maybe what the Brown > Black wire is for, but not sure. Don't have the wiring diagram to check

Hope that may help you

Graham

 

[wilsonny]

Thanks for the reply Graham and suggestions on where to test. I've managed to find a couple of pics in the meantime by searching the Internet. ..I'm currently mulling over comparing these pics with the wiring diagram. It looks like there are some interconnections between the terminals on the windscreen. I'll post an update if i get it cleared up.

 

[Simon P]

Has spurred me on to go and find out why mine has stopped working!

 

[wilsonny]

good luck Simon. ..I've not got any further yet, but here are the couple of pics I've found helpful. ..One is a wiring diagram, but I'm not sure it's the 993 one, I'm planning on checking this today; the other is a picture of someone else's car, but sadly the quality is not so good for zooming into the detail of the wiring.

 

[Graham-S]

Andrew

Looks like a 2 stage demist from the Wiring drawing

Red/White to Brown 1 feed
Red/Black to Black & Brown 2nd Feed

Does the switch have 2 positions? My old 82 Targa did. The switch pulled out a little way for stage 1 and fully out for stage 2

My 993 Targa is just 1. On or Off

Graham

 

[wilsonny]

hi Graham. There's just an on and off but I've read that there's a timer involved in the relay so that the separate heating stages don't fire up initially at the same time (supposedly to avoid the risk of the glass shattering)...Can't find the link to that write up at the moment.

 

[JB 3.2]

My understanding is that often its a Tracker which has been fitted and this may involve making alterations to the wiring loom on the back shelf.

Where are you located? it might be worth looking at another cars wiring.

 

[wilsonny]

Hi John. You could be on to something there, my vehicle folder does mention a tracker being fitted in the past. I'm in Cumbria. ..have to talk nicely to another 993 owner at our next meeting..