Hello Pagoda Group,
I'd like to thank all those members below who kindly responded to my post. In addition to those, who have further assisted me in my factory correct 280SL restoration endeavors. So, I figured, I should at least extend the courtesy and offer a correction on how to install a "Heated Rear Window Defrost Wiring Harness" according to Mercedes-Benz factory specifications.
In full disclosure, this post initially began several years ago when I was trying to remember how this original wiring harness was routed along the interior contours of my vehicle. Since then, I have made great progress with my 7 year - Bolt & Nut Restoration. I am literally at the end of the tunnel and can hardly wait to drive her. Just buttoning up the last loose ends.
HEATED REAR WINDOW WIRING HARNESS
The "Heated Rear Window Wiring Harness" sometimes referred to as the "Defrost Wiring Harness" is considered Special Equipment in Mercedes Benz technical manuals. According to Mercedes-Benz there are two version of heated glass available; composite safety glass (Sigla) and Laminated safety glass heat-insulating (embossed, Sigla). And, depending on the manual, the wiring harness may be referred to as an Additional, Auxiliary or Supplementary harnesses. (Note: For the remaining purposes of this Topic we will refer to the "Heated Rear Window Defrost Wiring Harness" as the "Harness").
CONSTRUCTION & COLOR CODING
The construction and the wire color coding of the "Harness" is depicted in (Fig. 1 of 3) provided below.
ROUTING & INSTALLATION
The routing of the "Harness" is depicted in (Fig. 2 of 3) provided below.
The "Harness" connects to the vehicle at a total of (7) locations.
(Note: There is no timer relay in its original configuration - that feature was installed on other Mercedes models a later model SL's.)
The "Harness" is connected to the Main Fuse Panel at Fuse No.2(o) and ground at the inner dash "ground spot" directly behind the dash to the lower right of the speedometer and lower left of the radio. [(o) = Output].
Ostensibly, there are only two viable choices either (Fuse No. 2 or No. 6) since they are the only positions which contain 25A fuses on the main fuse panel. The former position is further supported by the BBB service manual which mentions the supplementary fuse box for options such as the "Heated Rear Window" requires (16A) and may be confirmed in (Fig. 3 of 3 ) or on (Pg. 15 . 54 . 82-0/5 of the BBB).
The "Harness" additionally connects to the Supplementary Fuse Box within the engine compartment to the left of the Break Booster. This connection requires a Red (16A) Fuse, preferably copper.
The perpendicular portion of the "Harness" then runs down the back of the firewall over toward the heater blower motor on the drivers side footwell and down along the transmission tunnel anchored in place with aluminum tape so as to not interfere with carpet installation.
It continues down along the top lefthand side of the transmission tunnel passed the emergency brake (checking for proper clearance) and 1/4" to the left of the shift gate with just enough harness so that 4-pole connector can be easily be connected to the switch mounted in the center wooden console.
From there, the harness continues along the center tunnel toward the back of the vehicle and down to the floorboard traversing behind the driver's seat again as illustrated by (Fig. 2 of 3). Once more, I anchored the "Harness" in several place along this path until it reached the far most left rear corner of the floorboard. It then climbs up to the sill and into the B-Pillar Box following the main rear wiring harness.
From there the "Harness" is pushed thru the hole behind the upholstered of B-Pillar panelling and the remaining 2-Gang connector is installed so as to properly connect to the Hardtop's female 2-Gang connection coupler.
Finally, carpet is installed over the wiring which provides additional anchoring.
OPERATION
The switch is manually controlled either by pulling-Up for "ON" or Pushing-Down for "OFF".
(Note: This means it will remain engaged until manually shut-off since it is not connected to a time relay.)
