I just completed my installation of the Pertronix conversion kit to replace my points system.
I did considerable research on our forum to figure out how to do it, and what Pertronix unit and coil I should use on my late model 280SL. I had mixed results but enough of what I read led me to go ahead and try it myself.
The biggest difference in my late model 280SL is that for 1970 and 1971 years, transistorized ignition was used by Mercedes to help extend the life and performance of the points system. Well I had several frustrating experiences with it still burning up points and keeping a consistent Dwell setting of 30 degrees. It was also very difficult in my opinion to set the correct dwell which affected my timing and air and fuel adjustments.
Bottom line I decided to convert to the Pertronix electronic system.
It was very difficult finding what unit to order from Pertronix because my year and model was not listed on their website search function to purchase the correct one. I read in my research many horror stories with the install because Pertronix sent them the wrong unit to begin with.
I called Pertronix and spoke with their technical unit and found out that they match the unit to the distributor number in your car. Mine is what we call the 062 Bosch distributor. They said to order the Pertronix 91863 Ignitor II unit and highly recommended their Flame-Thrower II 45011 Coil. It specs out at 45000 volts and a resistance of .6 ohms. These set me back for $235.
The next challenge was figuring out which ballast resistor should be bypassed since the transistorized system had 2 resistors and how to do it. One resistor was a .4 ohm and the other was a .6 ohm. All my research said bypass "the resistor". Well perhaps other years had no resistor at all or they only had one. I didn't want to screw up my Transistorized Ignition module so I called the technical unit again. Spoke to a guy that said to only bypass the .6 ohm one because "you didn't want to burn up the module". Glad I called!
The instructions were pretty good on how to disconnect my points and condensor and to install the Ignitor. Got it all installed and went to start it and it just cranked over and over and would not start. Called technical again and got a different guy and he said to bypass all resistors. He sent me some tests to perform first to rule out anything else because he and my first guy could not agree on how many resistors to bypass. Did the tests and called back to help me interpret the results and got a third guy. He reviewed the notes on their system and asked me if I had a Mercedes with the transistorized ignition. I confirmed and he sent me the attachment below showing the before wiring diagram and the Pertronix completed wiring diagram.
To summarize the bottom line is that you do not bypass any resistors and just hook up the red and black wires of the Ignitor. The red "positive" wire connects to the inlet side of the .4 ohm ballast resistor and the black "negative" wire connects to the "-" side of the coil.
Car fired up right away and after adjusting the timing and the air and fuel mixtures my car runs better than it ever has with more power and much smoother as well.
