Classic/Antique Car Repair: QUESTION COIL / DISTRIBUTER

Question
Brad Hi I have two questions,  first its  in regards to a coil. Im using a test light . I have read to place one lead to the primary,  no matter which side of the coil I touch the test light goes on. Which side is consided the primary. The key side or non key side.   My second question is in regards to the distributor how much play should there be in the roter / shaft. Thanks again for your help Ken

Answer
It depends on the polarity of the cars electrical system. Most 12 volt cars are what is called negative ground. On most 12 voltsystems the neg side of the coil goes to the distributor  point. The reverse is true on positive found systems. With the key on on a negative ground system the positive side of the coil will have voltage all the time the key is on. The negative side of the coil will have voltage only when the points are closed. Did to side play should be no more than just preceptable.