The Stovebolt Site Forums The Shop Area Engine Shop What is Starter Motor Reversing Switch

I have a 1948 216 in a 1951 pickup. On the starter right behind the starter solenoid there is a switch. From what I see in catalogs (Obsolete Chevy Parts Co.),it is called a Starter Motor Reversing Switch? I am finding they where used until 1948. What is the purpose of this switch? Why didn't they come on engines after 48?

Most likely you are referring to the ignition reversing switch?

" The switch is mechanically actuated when the starter is actuated  to reverse the polarity of the ignition system on these vehicles. "

Not that I know what this does. Someone posted a good explanation this year. Maybe they will post it again here.

http://chevy.oldcarmanualproject.com/shop/1947truck/47ctsm1228.htm

If I remember correctly, on the 41-47 series engines, the distributor was not naturally grounded. The reversing switch controlled which way the current flowed through the points, so that (theoretically) there was an "even" amount of wear on each side of the points when they closed. (as is, because the current flow is all one direction, one side of the points wears out faster than the other side - I'm sure there's some fancy name for this phenomenon - "electro-carbon-fracturaization" or something! ;-) With the reversing switch, each time the truck was started, the switch was flipped mechanically, so that the direction of electron flow flipped directions, thereby causing even point wear, and longer-lasting points. Theoretically.

Eventually, someone at GM came to their senses, and realized that this over-thought solution was more expensive than the problem it "cured" in the first place. GM published a bulletin explaining how to take the switch out of line, and add a grounding jumper to the distributor.

Or so I assert, anyway . . .

-Michael

Michael,

Good explanation, I think.

I have a copy of that Service Bulletin (I read it about 2 weeks ago). I'll see if I can find it.

The polarity reversing switch was supposed to equalize metal transfer between the points by switching the direction of current flow at every operation of the starter. Eventually, somebody figured out that metal transfer was caused by the capacitance of the condenser being incorrect. The polarity reversing switch was an over-complicated mechanical solution to a relatively simple electronic problem.
Jerry