Author Topic: Alfa 75 A.R.C. pinout question  (Read 2866 times)

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SDMN

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Alfa 75 A.R.C. pinout question
« on: August 10, 2020, 07:47:26 PM »
Hello guys

I'm currently re-taping the wire harness behind the dashboard and found a loose wire, after a continuity test I came to the conclusion that it's the gray and black wire from the ARC pannel

Can anyone tell me where that wire is supposed to go, pics bellow?

https://i.imgur.com/2VUUQxI.jpg
https://i.imgur.com/GlXKiXv.jpg


thank you

Colin Edwards

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Re: Alfa 75 A.R.C. pinout question
« Reply #1 on: August 11, 2020, 10:31:58 PM »
Hi SDMN,

See if you can get to "Craigs Place" - see below link.

http://www.users.on.net/~craigf/

You'll find most of the 75 electrical schematics on this site. 
Download Group 40 and Group 43 files.  Also download the Group 43 file "Cluster and Electronic Instruments" on the Alfa 90.

The ARC display is labelled "C11" on the schematic/s.  ALL conductors from the C11 ARC display (connector "H") connect directly to connector "E" on the "N22" "Alfa Romeo Control".  My schematics do not support the cable colour scheme in your photo.  Assuming the black conductor code "N" is ground, the duties of the respective wires connected to the ARC display are as follows - N = GND, grey "H" = +15/54 pos, green black "VN" = light illuminating under panel, yellow "G" = data line, blue black "BLN" = "available" (no connection / ploarising pin), white black "BN" = alarm reset key, grey black "HN" = clock (clock pulse not time clock!), pink "S" = strobe. 
Given the above, I'm suprised your grey black "HN" clock wire is termnated with a female spade lug.

The above will make a lot more sense if you have the schematics in front of you.  The 75 is electrically pretty straight forward if you can lay your hands on the schematics. 

Is your ARC functional or performing like xmas lights?  Lots of very helpful info on the net re getting the ARC working 100%.  Replacing a voltage regulator fixes 90% of the issues.

Colin

Present
2020 Giulietta Veloce
2018 Abarth 124 Spider
1987 75 3.0

Past
2015 Giulietta QV
2009 159 3.2 Ti Q4
2012 Giulietta TCT Veloce
2006 147 Ti 2 door Selespeed
1979 Alfasud Ti 1.5

SDMN

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Re: Alfa 75 A.R.C. pinout question
« Reply #2 on: August 11, 2020, 11:10:05 PM »
Hey Colin, thank you for your reply

If I understand correctly all wires from the ARC display must connect in this module https://i.imgur.com/qTUIRAU.jpg correct?

If so it does make very little sense to have a female spade terminal in that wire, but this harness has been messed with before (lots of homemade splices and taping). I initially thought it might connect to that ground cluster that uses spade terminals on the left of the steering wheel (LHD car)

It's wierd because everything seems to be working fine, even with the loose wire, it just pains me to put the dashboard back in place knowing that theres a wire not connected behind

*edit, it does have a diferent pinnout colour compared with the workshop manual. this manuals are from 85 my car it's a 91 model, could alfa have changed it in that period? seems unlikely
« Last Edit: August 11, 2020, 11:17:51 PM by SDMN »

Colin Edwards

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Re: Alfa 75 A.R.C. pinout question
« Reply #3 on: August 12, 2020, 10:20:40 AM »
No problem.

Yes.  All wires from the ARC display module "C11" should connect directly to connector "E" on the "N22" ARC module.  The black "N" Gnd wire possibly loops around a bit so as to pick up a half decent earth / -ve.  Seems a rudimentary serial data signal is clocked into the C11 ARC display so fair to assume the N22 ARC module talks to the C11 display and nothing else.  All other display signals appear to be driven discretely.

The spade connector is a bit of a worry.  If everything sees to work ok I'd leave it alone or confirm again 100% what it connects to.  I pulled out about 6kg of redundant cable the PO had added when installing some monstrous sound system!  Worries me when wiring gets attacked by people not having access to schematics.

Toyota (in the 70's and 80's) seemed to me to be the only manufacturer to publish schematics you could pretty well trust 100%.

 
Present
2020 Giulietta Veloce
2018 Abarth 124 Spider
1987 75 3.0

Past
2015 Giulietta QV
2009 159 3.2 Ti Q4
2012 Giulietta TCT Veloce
2006 147 Ti 2 door Selespeed
1979 Alfasud Ti 1.5

pasey25

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Re: Alfa 75 A.R.C. pinout question
« Reply #4 on: August 12, 2020, 01:52:35 PM »
When I worked for one of the large OEMs the number of changes we made to wiring harnesses through production was higher than anything else in the car.
Current:
1969 Lancia Fulvia 1.3s Coupe
1967 Lancia Fulvia Berlina GT 1216cc
2017 Abarth 595 Competizione
1991 Alfa SZ #440

Past:
1967 Lancia Fulvia Berlina GT 1231cc
2005 147 GTA Monza Selespeed 59/100
2001 156 Monza Selespeed Twin Spark
2010 159 TI 2.4 Sportwagon
1991 Alfa 75 Twin Spark