Re: Packard R11 overdrive and Kick down switch question

Posted by HH56 On 2019/6/28 21:18:06

You are correct in that the kickdown action could kill the engine but due to a sequence of operation and close timing between various contacts the ign is only shorted a very brief time.

When the OD completely engages the solenoid plunger extends the pawl into the sun gear and by that action the cutout contacts inside the solenoid close. Ground is then present at one of the terminals on the kickdown switch but that set of contacts in the switch is open so ground goes no farther.

When kickdown is desired and the accelerator is pushed all the way to the floor the kickdown switch does two things. When the plunger in the switch starts to move the first set of contacts near the plunger open to drop out the relay and by that action, the solenoid loses power. With the continued movement of the accelerator and plunger, a brief moment after the relay and solenoid lose power the second set of contacts in the kickdown switch close and the ground passes thru the kickdown switch to the coil terminal and shorts out the distributor pulses.

When the ignition quits, almost instantly the engine loses power. By losing engine power the torque or pressure the sun gear is exerting on the pawl is relaxed and with the solenoid off, the spring inside the solenoid can retract the plunger and pawl. As soon as the plunger moves back into the solenoid the closed cutout contacts open and ground is removed from the kickdown switch and ultimately the coil so engine starts to run again. You are also out of OD because the pawl is no longer holding the sun gear. The entire sequence only takes a few milliseconds to complete so the engine never has a chance to stop rotating and die before the spark is established again.

If there is a mechanical problem and the solenoid takes too long to retract, conceivably the ign would be shorted long enough for the engine to die. As a second protection, if the engine starts to die instinct would have the operator working the accelerator. As soon as the accelerator is relaxed and moves away from the floor the cutout contacts in the kickdown switch would open also removing the ground to the coil and the engine would stay running.

In the kickdown sequence, once the reason for kickdown is over such as needing more power when passing a car, if the car is still moving above the governor cut in speed the OD will also be ready to re-engage when the accelerator is released. If OD is not desired again it will be necessary to lock OD out via the knob on the dash.