Pertronix wiring - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 01-20-2007, 09:39 AM Thread Starter
BenzWorld Junior Member
Date registered: Dec 2006
Vehicle: W114 250C
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Pertronix wiring

I've installed a new Pertronix ignition on my '72 250C but the care won't start. Pertronix's instructions are not clear and complete in my opinion as they don't tell what I'm supposed to do with the existing wires to and from the existing 4 and 6 ohm resistors or the wires going to the existing ignition control unit. Since it was pertronix that selected the model for me based on my distributor type I figured they'd have complete instructions for my vehicle. Can anyone out there help me?
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post #2 of 3 (permalink) Old 01-20-2007, 10:38 PM Thread Starter
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Date registered: Dec 2006
Vehicle: W114 250C
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Figured it out myself

I figured the wiring out for myself with no help from Pertronix or all you geniuses. So anyone putting in a Pertronix electronic ignition and flame thrower coil in a '72 250C with two resistors one a .4 and the other a .6 ohm, here is what I did to make it work.
Step 1 - Disconnect the wires to and from the .6 ohm resistor which should be the lower one if the engine hasn't been messed with. The wires coming to the resistor on one side is from the ignition control unit, the other side goes to the coil. Save the coil wire for use later. Discard the .6 ohm resistor, you don't need it.
Step 2 - Disconnect the wires from the .4 ohm resistor. The wires coming to this resistor on one side are from the ignition starting switch, the other side goes to the starter and ignition control unit.
- The ignition control unit and the wiring harness going to it can be removed and used as a paper weight if you like. You don't need it.
Step 3 - Connect the Pertronix red wire and the ignition starting switch wire to one side of the .4 ohm resistor.
Step 4 - Connect the wire you saved from step one and the wire that goes to the starter to the opposite side of the resistor as the Pertronix red wire and ignition starting switch. Connect the wire you saved to the positive side of the coil.
Step 5 - Connect the Pertronix black wire to the negative side of the coil.
Your done. My car started right up and had no hesitation or hickups at all. Hope this helps someone out there.
This is basically what Pertronix's directions show except what to do with the ignition control unit, ignition starting switch and starter wires.
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post #3 of 3 (permalink) Old 01-21-2007, 07:15 AM
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Date registered: Oct 2005
Vehicle: MBZ '87 300SDL, MBZ '85 380SL, RR '77 Silver Shadow II, MBZ '98 E300TD
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Well done Idahomike. I've had similar experiences with Pertronix tech support and like you found their written instructions nearly useless. I recall wring a 280SL with a Pertronix in which I cut off the .4 ohm resister, the one you kept, because the coil I used (might have been the 45K flamethrower) was internally ballasted already and didn't need it (.4 ohms internal resistence if I recall).

In any case, cheers and good luck to you.
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