1979 Dodge Truck Intermittent spark

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check your voltae regulator. its usually on the firewall. just take it off, and look at the back. normally its a metal housing that contains the circuits inside, which are surrounded by this plasticy stuff. look at the back, and see if its melted at all. i had a similar problem with my 79, and turns out that voltage regulator was fried.

now that I think about it, I believe the you are experiencing is a faulty ballast resistor, on the firewall between the steering column in the Fender, it is easy to identify it is white porcelain 4 by 2 inches, with four wires connected to it, two on each end, it is easy to check, turned the key on and make sure you have 12 V going into the resistor, and I can't remember how much coming out I think 10V or 8V

it turned out to be a cheap chinese part. turns out that the new voltage regulator i bought didnt have continuity between the clip for the plug and the outer housing, depriving it of a ground, so it wasnt charging. now i have a new problem, it idles real rough occasionally.....