Ballast Resistor Wiring

[ejmatushek]

I just purchased a 1966 230SL which started up instantly when I took delivery. I was cleaning up the engine compartment, and saw the ignition ballast resistor laying loose outside of the retainer clip. I placed in back in the retainer clip and now the engine cranks but doesn't get spark and won't start.  I noticed I have a second wire attached to the terminal of the ballast resistor that is connected to the ignition switch but is not connected to anything on the other end.  The other terminal of the ballast resistor is still solidly connected to the positive terminal of the coil.  Does anyone know what this loose wire is for, and is it supposed to be connected to something?  I have attached a photo.

[Paul99]

I have an early 230 as well.  I found that they have a ballast resister, but doesn't do what later cars do, that is there would be second wire from the starter so when cranking the ballast is bypassed giving higher voltage.  Very early cars didn't have the extra wire, so it should be just one live feed to one side of the ballast, then the ballast then the wire to the coil. Very simple.  (unless someone put the later starter with the ballast bypass option on your car?)

You said you put the ballast "back" into a clip?  Would that be shorting out the wire some how?  Take it back out loose and if it runs, thats the answer.   Hope that helps a bit.

[ejmatushek]

Nothing is shorted.  I'm wondering if a prior owner added a jumper wire to by-pass the ballast resistor for starting.  But I can't find any broken wire strands on the coil or on the distributor positive terminals.  There is 12 volts coming from the ignition wire when the key is switched on, and that wire is attached to the first terminal of the ballast resistor; the same terminal that I see a loose jumper wire attached.  Seems strange that the car won't start at the same time I noticed a dangling wire connected to the ignition ballast resistor.

[kampala]

Ejmatushek,

since you are a Full Member, you have access to the color wiring diagrams that Achim has provided.

https://www.sl113.org/wiki/Restricted/ColorWiringDiagrams


It does seem odd that you have this extra wire on the ignition side of the resistor.  This would mean that this additional wire has power when ignition is on and sounds a bit dangerous if it were loose.    If someone placed that wire they were probably either trying to by-pass the resistor or wanted to supply power to some other item.   

You mention that you no longer get spark.   Check that you have power, with ignition on, going to the coil from the other side of resistor (does power make it through the resistor?). 

It will make it much easier for others to help if you explain what distributor / ignition system you have as it may have been changed.  If you are not certain, provide close photos.   

good luck and be careful with that loose wire as you are close to fuel sources.   

[ejmatushek]

Found the problem. I tested the 50 year-old ballast resistor and found it had no continuity.  Some genius used the wire as a jumper instead of replacing the part, and it came loose when I was cleaning up the engine compartment.  I replaced the ballast resistor and it starts like new.