Ignition (electrical) switch question.

[69427]

Mike -
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"...In the RUN position, the ignition primary circuit is activated through the resistance wire and the air conditioning, heater and defroster circuits are activated... I agree.

"...When the ignition switch is turned to the START position, the ignition primary circuit is activated directly, by-passing the resistance wire, and the starting motor is activated to crank the engine."

I'd say that's pretty crystal clear... I didn't make that up. Well, at the risk of appearing difficult to deal with, it's still unclear to me. :amused: In electrical design, you can bypass something without disconnecting it. In my mind, the switch would be designed so that in either "Crank" or "Run" position, there is 12 volts at the pin connection that goes to the ballast resistance and the coil C+. During cranking, the "Crank" output from the switch would also go hot, and power up the starter solenoid causing the plunger to move. (Lots of this is obviously basic. I just ask your patience through all this.) When the plunger comes back and forces the contact ring/disc back, we then get a connection from the starter battery line, through the disc to the little contact finger, and then on to the coil C+. The current (from the battery) will go to the C+ terminal, bypassing the ballast resistance due to a simple principle. There is 12 volts on both sides of the ballast, and a resistor requires a voltage differential for current to flow through it. The ignition switch can have 12 volts on the ballast feed pin 100% of the time, and the ballast can still be bypassed on occasion (as in cranking mode).
............................ I'll be glad to fax you copies of this original GM literture if you want it.

Lars

Lars, I do apologize for how much of yours and everyone else's time I've consumed with this question. I worked for Delco for 24 years as a design engineer, and I just like to be able to understand how my car is designed and wired.
I may be able to use my wife's work Fax to receive a drawing or two. I'll talk to her and let you know.
Once again, I do appreciate all your time and help you've provided. This switch is an oddball thing to be interested in, but it's just the way my brain works. :amused:

 

[Garys 68]

Huh, never knew about the dual circuit. My 68 dash mounted switch had been replaced an apparently is the HEI design. I know both circuits were energized when cranking. BTW, the replacement switch didn't line up with the plastic plug tabs (Chinese stuff probably).

BB-
I'm not slamming you - really. I'm just pointing out that your 79 service manual info will not contain the pre-75 dual-circuit info that Mike was trying to get info about. Many people think that all the C3 wiring stuff is pretty much the same (as witnessed by the "consensus" voting on how it must operate, earlier in this post), but there was a big change when GM went to HEI, especially in the cranking/ignition circuit, which included a complete re-design of the ignition switch and its cranking operation. Most parts houses (including NAPA) now sell only the HEI type ignition switch, because you can use the HEI switch in both points and HEI cars. But you cannot use an original points ignition switch on an HEI car... The majority of our cars have probably had their switches changed by now, so if you "ohm" one out, it will likely show parallel circuits. But the original switches did not have parallel circuits.
Lars