'73 Power Shut Down While Drving

I have a '73 350 w/ Auto Trans. Tonight while driving along, the car cut off, the headlights went off - no power at all. I coasted for a ways so I
could get out of the way - after about 30 seconds - power restored and the car cranked and ran fine. I was running AC, radio and headlights. I turned off AC but it happened a 2nd time while sitting at a stop light - power all shut down - then about 30 seconds late - all restored. I have had it happen in the past when it was raining - radio, headlamps, windsheild wipers and AC running.
I figure that there must be a short somewhere and the system is getting overloaded? Any ideas. I would love to fix - it is kind of dangerous.
Thanks, Chris
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If you are still running the original points distributor, I would check the capacitor. Make sure it has good contact with the strap and plate. It's a very inexpensive part, replace it, and you can check it off the possible cause list.
Brian

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Actually, I istalled an electronic distributor a couple of years ago - boy what a perfomance difference that has made!

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Check battery terminals and ground strap from battery to frame / motor to frame.
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C3s have some fusible links that can break with age as a fusible link is a section of wire smaller gauge than the rest of the circuit. It is possible that this has happened and as you have road vibration and heat, the wire "opens" and you lose power. Then after 30 minutes of cooling, it closes again and you run.
In some C3s, these are near the horn relay. In others, they are near the starter. Check with a voltmeter or test light while flexing the wire. You can buy the links at Chevrolet with the kit to install the big black lumpy splice, or simply install a 3 inch piece of wire one or two gauges smaller (numerically bigger) than the regular wire. For example, if the wire is 12 gauge, install a 14 or 16 gauge section.

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