Re: 39 Packard OD solenoid

Posted by HH56 On 2022/3/24 10:46:23

Like most Packard wiring diagrams -- particularly prewar drawings -- they may depict how something physically looks but as far as function goes they treat almost all switches, relays, solenoids etc as black boxes with nothing but wires going in or coming out. Rarely is anything drawn on a wiring diagram to show things like coils or contacts that are internal in the boxes. For that info you need to go to something like training manuals or aftermarket books.

If you check the solenoid cut away drawing in post #20 of this thread you will see the normally closed pull in contacts which are located inside the solenoid case. The contacts are activated by the small push rod which the main plunger hits and pushes outward as it reaches the end of its travel.

In the solenoid internal wiring diagram shown in post #22 you will see the two coils in parallel. Both coils are fed from the SW terminal and when the solenoid has pulled the plunger in and it hits the push rod, the normally closed contacts in the pull in coil circuit will open and turn off the pull in coil leaving just the hold coil active.