Okay. See if you can make sense out of these. The first one shows the wire colors, and the parts are labeled. This is from a "Notes Pages" handout I gave to my students. It looks real complicated because of all the things I added. The second one shows just the ignition switch and neutral safety switch turned on. The lame-brained engineers added a Rube Goldberg circuit by adding the Engine Computer, (PCM) in the same circuit as the neutral safety switch. That means you can no longer perform a simple, quick resistance test to see if the switch is working properly.
In the third drawing, the relay contacts have clicked on and current flows through the two coils in the solenoid. Some current goes right to ground, and some goes to ground through the very low resistance starter motor coils. The magnetic fields of the two coils are strong enough to engage the starter drive gear. The solenoid contacts turn on at the same time.
In the last drawing, the high starter current flows through those contacts, (which cause a lot of trouble), and through the motor, to ground. Full battery voltage is on both sides of the Pull-in coil so it turns off. It isn't needed once the drive gear is engaged so by switching it off, that current is available to the starter motor. That might make the difference between starting and not starting on a cold day or with a marginal battery.
Images (click to enlarge)
Wednesday, May 11th, 2011 AT 7:22 AM