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kdjones2000 kdjones2000 is offline
In the Fires of Hell.....
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Join Date: Oct 2007
Location: Phoenix, AZ
Posts: 2,980
Wiring Things Up

Once the lenses are modified and installed, the next step is to wire them into your car. This is actually the tricky part of things, as there are many, many ways to do this. A look though threads here at Pelican as well as on the "other forum" reveal that the vast majority of people create their own harness, usually using a #53 type 40A relay wired into a secondary foglight switch installed into the empty space near the headlight switch. This is what Jon did on his car:

While this is certainly a way to make the DL's work, I wanted a more "elegant" solution for this, one which would work the way I wanted it to. Going through the various scenarios I came to the conclusion that I wanted the foglights and DL's to work with the following logic:

I didn't want to have to be throwing a driving light switch every time an oncoming car came into view, yet I also wanted to have the ability to use the DL's as replacements for the popup headlights when I chose. The above satisfies those requirements.

After poring over the various wiring diagrams for the '88 model year cars, I was able to pull the following information that was relevant to the foglights:

1) The USA spec cars use relays in both the Foglight and "Complimentary Light" locations, but the "DL" relay is there really only to allow for the "flash to pass" feature to work, when the foglight switch is in the Off position.

2) The ROW cars use a SPST relay in the DL location (G12) in place of the US SPDT relay. In all cases the DL's are hard wired into the 56a circuit so that they will come on with the high beams or using the "flash-to-pass" feature. Different countries have different wiring though the Bridge Adapter (G6) for the foglights, presumably in order to comply with specific regulations.

3) As mentioned in the Panorama article about converting to Euro foglights, the Bridge Adapter is an important element that determines how the foglights and DL's work. There are 10 different versions of this G6 part.

The wiring for the various USA and ROW combinations are summarized in Page 12 of the wiring diagram. From this it can be seen that the JAPAN version of wiring is the closest one to the USA version, but with the additional connections for the DL's:

4) Even for the USA wiring harness, provisions are there for the DL's, with all of the connections present up to the Central Electrics box, coming out at C21 and C31 (Area B-6 on the drawing below):

What this means is that the DL's can be wired directly into the existing OEM wiring harness, using the OEM relays and locations inside of the fuse box. All that needs to be done is to modify some elements of the Bridge Adapter (G6), make some wiring changes around the G12 relay and the Headlight/Foglight switches, and add a good wiring run from the central electrics panel down to the DL locations.

After going through all of the details of analyzing the diagrams above, the following modified wiring schematic should provide the logic shown in the table above. The strategy is to use Circuit 57 to control the foglights and DL's with Parking Lights on, 56b using Lowbeams, and 56a with Highbeams and the Flash-to-Pass feature:

I have verified that the Bridge Adapter wiring works as it should per the schematic, but I am still looking for some parts to finish up the wiring (See my WTB in the Classified section), but I am reasonably confident that this should work as planned.

That's it for now; I will update this as progress is made.
NASA/PCA Instructor
'88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again

Last edited by kdjones2000; 05-25-2018 at 03:51 PM..
Old 01-24-2018, 05:15 PM
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