Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

248 Chapter Eleven
Figure 11-44.
Typical distributor rotors.
Figure 11-42. When coil connections are reversed,
spark plug polarity is reversed.
Figure 11-45. A Hall Effect triggering device attached
to the rotor. (Courtesy of DaimlerChrysler Corporation)
Figure 11-43. A distributor rotor and a cutaway view
of the distributor cap.
the spark plug electrodes in the cap. The key may
be a flat section or a slot in the top of the shaft.
Delco-Remy V-6 and V-8, shown at the left in
Figure 11-44, are keyed in place by two locators
and secured by two screws. On the right is shown
a plug-on or push-on distributor rotor. Most other
rotors are pressed onto the shaft by hand. The rotor
in a Chrysler optically triggered distributor is
retained by a horizontal capscrew.
Rotors used with Hall Effect switches often
have the shutter blades attached, Figure 11-45,
serving a dual purpose: In addition to distributing
the secondary current, the rotor blades bypass the
Hall Effect magnetic field and create the signal
for the primary circuit to fire.
Rotor Air Gap
An air gap of a few thousandths of an inch, or a
few hundredths of a millimeter, exists between
the tip of the rotor electrode and the spark plug
electrode of the cap. If they actually touch, both
would wear very quickly. Because the gap cannot
be measured when the distributor is assembled, it