Re: Stewart's 1955 Packard 400

Posted by HH56 On 2016/2/2 19:50:09

You need power to the center terminal of control switch. Ground is provided thru the case being bolted to the frame.

When you move the switch lever one direction it closes a mechanical contact and energizes one of the heaters to start bending its bimetallic strip. After about 7 seconds or so the bimetal will bend enough to touch another contact and bring in one of the relays. When the relay closes it connects a solenoid terminal to ground and motor starts going. Other things happen in the switch between the relay, heater, and bimetal contacts but that is not important for this description. The important part of what else happens is the relay will stay energized until the switch lever moves back to the center position and disconnects the first or mechanical contact.

Moving the lever the opposite direction repeats the cycle with a different mechanical contact, heater, bimetal strip contact and relay to move the motor the other direction.

The time delay is kind of arbitrary. Packard said 7 seconds but in reality it has been reported as low as maybe 5 and some have said theirs typically runs over 10 seconds. I suspect it has to do with the actual voltage the heaters are receiving.

The limit switch does need to move freely. It may be possible to bend the actuator bar slightly to clear whatever it is touching but be careful. I don't remember if the actuator mounts to actual metal in the switch and can take some pressure or mounts to the fiber board holding the contacts.