ballast resistor

[rob walker]

I am trying to get to the bottom of why I am having a hesitation at revs. The car is running elecronic ignition but the garage that is trying to sort the problem noticed that the ballast resistor is disconnected.
What impact would having the ballast resistor disconnected have when running electronic ignition?
Why would someone disconnect the ballast resistor anyway?

[mdsalemi]

Rob,

Each electronic ignition system has it's own ballast requirements.  Mine is disconnected now as there is enough ballasting per requirements in the coil itself.

[Benz Dr.]

The ballast resistor protects the coil from overheating if you turn the key on and the points are closed. Since they're almost always closed when the engine is stopped the resistor is needed.

The electronic system has no points so there's no danger of coil over heating problems. The resistor reduces primary voltage going to the coil. Somewhere around 8 volts.

[mdsalemi]

While the COIL may not overheat with an electronic system, the electronics can; Pertronix specifically states do NOT leave your ignition ON or in the RUN position without the engine running.

[Mike Hughes]

Hi, Dan -

If the ballast resistor reduces promary voltage to the coil down to 8 volts, would bypassing the ballast resistor generate a hotter spark (stock points & condenser system)?

[Benz Dr.]

It will produce a hotter spark and that's just what they did. On later 280SL's they ran a wire from the starter solenoid over to the coil. When you hit the starter the ballast resistor is by passed and it will send 12 volts ( or more ) directly to the coil to aid in starting. I think it works too because these cars generally start well if everything is working properly. The earlier cars can be a bit finicky by comparison.

[Mike Hughes]

If one wanted to run a wire on an early car (like my 230SL) from the starter solenoid to the coil (to duplicate the late car starting aid) how would you recommend going about it?

[Benz Dr.]

I suppose you would run the wire from the starter solenoid to the coil. On the late solenoids there are two terminals - one of the ignition switch wire and one that runs to the coil. If you don't have two terminals on the solenoid you can hook the wire on at the junction box on the side of the oil pan. You could tie strap the wire to the positive battery cable running around the front of the engine.