Or the return leg of the coil wiring is what came off.

Have you checked the wiring at the Resistor by the coil? The problem you mention is identical to what happens when the resistor is disconnected. You're actually engaging the starter, but at a point that it isn't making enough of a connection to allow the solenoid and hence the starter to kick in.

Have you done any work recently on the Tach? How about the coil/ distributor / resistor wiring?

When the key is in the RUN position, can you turn on the Heater Blower, the Radio, the Turn Signals?

Any one of these will help ID where ithe circuitry failed and IF it is in fact, the Ignition Switch.

Enrique

Or the return leg of the coil wiring is what came off.

Have you checked the wiring at the Resistor by the coil? The problem you mention is identical to what happens when the resistor is disconnected. You're actually engaging the starter, but at a point that it isn't making enough of a connection to allow the solenoid and hence the starter to kick in.

Enrique

Enrique, you are the man :knockedou ... What you said about the ballast resistor got me thinking so I went back and rechecked all of the wiring. Everything looked good. Next, I reinstalled the old ignition switch and bypassed the ballast resistor to see what would happen. The car fired right up and kept running. FYI I've been running an Allison electronic ignition in conjunction with that resistor for years and never had any problem.

Is there any definitive way to test whether the resistor is bad besides the car not running when it's broke? I put an ohm meter to it and could not get a reading between terminals - couldn't think of another way to test it. I also couldn't find anything in my repair manuals regarding testing the ballast - is there any pre-warning when one is going bad or do they just fail instantaneously?

Actually the way you tested it IS the way to check a resistor.

You put your meter on the Ohm setting (Greek Letter Omega Ω), put a lead on each end and you measure the resistance of the resistor. A Zero resistance would be an ideal piece of wire, but even straight wire will show SOME resistance (depending on the sensitivity of your meter).

An infinite resistance would be a blown resistor. You could also check for continuity. If there is no tone (presuming that's how your meter confirms continuity), then you have NO continuity and therefore an open circuit or a blown resistor.

With the electronic ignition, AFAIK you do NOT need the resistor. The ONLY purpose of the resistor is to reduce the voltage to the distributor from 12v (nominal) to 6v and therefore reduce the wear and tear due to pitting on the breaker points. No points, therefore no need to reduce the voltage. So, simply connect the two wires that went to each end of the resistor to each other, tape the connection to avoid a stray spark or short circuit and you're off and running.

As far as pre-warning...sometimes, usually none and what you get can vary depending on how it's failing, if it isn't an instantaneous failure.

Glad we solved it, now send the switch back to MSA, thank them for their willingness to receive it and especially for paying for the shipping. It isn't often that you see companies accept a mistake and do right by the customer, and when you DO see it, it makes you glad to do business with them.

Enrique