i had a similar problem as you with my speedo cluster. all of my lights were burnt out so that was the first problem and then i have to play with turning the light switch left and right to get the speedo lights to work. once i find a good spot they stay on fine, but it had me a little perplexed at first.
congrats on gettin a jeep and a 79 at that!
'06 Wrangler SE, soft top, hard doors, 2.4L, rolling completely stock and unmodified for the short term...
'10 Wrangler Sport, soft top, hard doors, 23S package, Teraflex 2.5" spring lift, Spidertrax 1.5" wheel spacers. Sold.
'79 CJ-7 Renegade, 258 I6, T150, D20, D30/AMC20, 2.5in Rancho lift, 31x10.5 AT's, TeamRush upgrade, flush tail lights - Sold :'(