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Failed Electric Windows and Odd Undocumented Red Wire Loop? - '81 911 SC UK RHD

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NeilH PCGB Member
2022/01/15 12:16:57 (permalink)

Failed Electric Windows and Odd Undocumented Red Wire Loop? - '81 911 SC UK RHD

Hi All
After occasional intermittent failure of the electric windows (never long enough to fault find) - they've finally stopped altogether. Better, in a way I suppose ;-)

However, on investigating, have found my wiring isn't following the '81 wiring diagram and is a real mystery! Have tried to find older and later diagrams - those I find still suggest mine's non-standard?
I'm wondering if anyone has come across this in case it is a factory thing as opposed to a later owner modification?
I've attached an image and diagram.
I seem to have a "mystery" red (gone pink?) pair of wires POSSIBLY looping out from the electric window relay's 12VDC output, going off somewhere into the loom and disappearing behind dash and fresh air blower box - before coming back to the input (top) of the correct window fuse 21!
This pink loop is open circuit, so I'm getting no 12VDC at the fuse input despite 12VDC being delivered by the relay correctly!
The pink wires are "odd" - in one respect they don't look quite as old as all other wiring (40-years old). But that said they are laid inside aged-looking black PVC sleaving along with other standard wires through the rear of the dash and elsewhere in the car. There's also many other runs of the same aged-looking black PVC sleaving carrying most of the rest of the cars wiring and I assume this is all "factory"? So I'm 50/50 on them being an owner\post factory modification....   
- Theory is - I could take the pink loop out of circuit, move the window relays 12VDC output to fuse 21 direct (as the manual suggests) and all should work.
- I will see if i get the confidence to do this as a test....
- But clearly I'm wondering what do I risk taking power away from?
Any confirmation if anyone else has come across this - or not - greatly received.
Best regards

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3 Replies

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chas3.2 PCGB Member
Re: Failed Electric Windows and Odd Undocumented Red Wire Loop? - '81 911 SC UK RHD 2022/01/15 14:46:05 (permalink)
Hi This mite help you.   Also look for alarm control boxes may have had total closing fitted
now not working.

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Current 911 997 2S 2008.
1987 924 S.
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geedee PCGB Member
Re: Failed Electric Windows and Odd Undocumented Red Wire Loop? - '81 911 SC UK RHD 2022/01/15 15:58:14 (permalink)
Sorry I have no answer to your mystery. I have a Haynes manual attributable to 911  65- 85, apparently no mention of pink as used as a wiring colour.  It seems that the circuit should be as you describe, minus the pink wiring.  I wonder if there might have been a thermal overload built into the circuit at a later stage..  I`m guessing the pink has the same gauge wire and insulation as the rest of the circuit to cause you to think it could be original.
If it is a mod perhaps there is something else that was installed to be powered from the mirror circuit and the link back on the other pink has failed.
I might just be tempted to bypass the pink given you have it backed up with a fuse just to try it out... carefully. 
Good Luck
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NeilH PCGB Member
Re: Failed Electric Windows and Odd Undocumented Red Wire Loop? - '81 911 SC UK RHD 2022/01/15 18:00:37 (permalink)
Thanks Charles and geedee 
Looks like alarm or immobiliser was a good call!
I noticed immobiliser LED low down on the dash seems to continue to FLASH while engine running and also driving - suggesting it's immobilised or possible "safe mode"?! I've caught it do this once or twice in the past wondering if I'd remembered correctly what it's state should be! Now doing it permanently while windows have failed. I reckon the pink circuit's been breaking down for a while and both immobiliser LED and windows would have failing at the same time
I removed the pink wires from the circuit and swung the relay outup over to liven fuse 21 - and hey presto - working beautifully! 
Too late in day to see if it fires up. Try tomorrow.
Many thanks
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