Help with 1971 Transistorized Ignition

[JimVillers]

I am working on David Hay's 1971 280SL.  It is being assembled after a full restoration and we are in the "final" phase. 

My current dilemma is the connection of the shielded green wire from the distributor.  It is not clear from the BBB where it goes.  The shielded green wire from the transistor unit goes to a relay component on the inner fender. 

[Tyler S]

Jim, Here is a simplified diagram from the tech manual. the wires with the dotted lines are the shielded wires.  Hope this helps

[Tyler S]

Here is another that shows how the shielded portion of the wire connects to the terminal block on the inner fender well.

[JimVillers]

Tyler .... I studied the diagram from the BBB but it is not what is in the car.  The two terminal block attached to the transistor unit has a green shielded wire that goes to a "module" on the inner fender.  The screws have never been removed and the wiring harness is original.

By looking at the book, that green shielded wire should go to the distributor. The other parts of the diagram appear to be OK; the power goes through a ballast to the red wire in the unit and the black wire from the unit goes to the resistor and then the positive coil terminal.  On this car, the green shielded wire goes from terminal 7 to a "module" on the fender.

There must be another terminal someplace. 

My guess would be that the distributor green wire would go to the same terminal as the green wire to the other "module".  It confuses me that the screw has never been removed (dirt and corrosion on the terminal has not been disturbed).

[Tyler S]

Being a late model it appears it has an rpm switch "module". Looking at the diagram link below, item 45 is the transistorized ignition and item 50 is the rpm switch. It appears the wire for the distributer goes to the terminal block 7 along with the other green wire for the rpm switch. So your hunch looks correct. Dont let dirt dictate where your wiring should be See diagram below
http://www.sl113.org/wiki/uploads/Electrical/280slwiringdiagram.pdf

P.S. It is all possible the ignition circuit was wired differently at some point because of a faulty transistor box. They can be wired like the older systems essentially bypassing the transistorized control unit. Keep this in mind if you have no spark with it wired correctly.

[JimVillers]

Tyler .... Thanks.  It is good to have another set of eyes evaluate the problem.

My second approach is to install a Pertronix unit.  The distributor is a Bosh 0231185010 which is not listed in the Pertronix catalog.  Has anyone figured out the correct unit for this distributor (1863?).

[Tyler S]

That part number is a replacement for the original 0 231 116 067 distributor.
On the Pertronix website ignitor search you need to input the distributor part number with dashes (0-231-185-010)
Pertronix kit is 1867A
Though I have had bad luck with Pertronix units. You may want to look into Crane or
123 IGN

[JimVillers]

Tyler .... I have had the opposite experience.  I have had two crane cam units fail on me and I have used Pertronix in four of my cars for many years and thousands of miles without a single issue. 

Thanks for the part number.