Tell me about your ballast resistor failure.

Turns out the situation was strange. I changed the ballast resistor with the same results. I ohmed out my resistor and it was the same as the new one. I checked voltage at the resistor with the key on and had nothing. Checked my choke wire and alternator and had battery voltage. I went back to the resistor and it suddenly had battery voltage. The truck started normally several times. Sticky contact in the ignition switch?? I'm grateful that it runs but not sure what happened. This was on my 75 D100.