Headlights and instrument lights flicker

I don't know much about the 1999 Frontier so you have to help me out here a little -- Is the headlight switch on the '99 on the steering column or on the dash ? Is your dash panel light dimmer built into the headlight switch ( where you pull the switch to turn the lights on and turn it to dim / brighten the dash lights ) ? If the switch is a combination like that, it is probably the switch. If the headlight switch is on the column ( and your dash dimmer is on the dash ), there is still a possibility that the problem could be the switch but I would start by bypassing the dash dimmer switch and see if that changes anything. Since your cig lighter was shorted out, it could have also damaged the connector in the dash dimmer switch ( the cig lighter was lighted and the light was also controlled by the dash dimmer ) and now the switch is shorted or not making a good connection which would cause the flicker. Don't forget to check all of your power and ground connections under the hood as well ( battery, alternator, starter ) and make sure they are tight / no corrosion. Hope this helps !