cold ’91 camry, no lights

Hello all, I recently purchased a 1991 Toyota Camry LE V6, and it is still quite the serviceable unit even with 204K miles on it - for a mere $200! I am hoping I can get some assistance from what I have been told is one of the best online sites for electrical repairs, diagnosis, and install to make that the best $200 I have spent in several years. The only major problems that the vehicle had when I purchased it were a dead short that killed the battery overnight, and the weirdest problem with the running lights I have ever run into. The dead short was an easy fix. The battery was junk, however the running light issue.... it's got me over a barrel. It's December. It's cold outside, and if the cabin temperature is at ambient the running lights, liscence plate light, and all dash lights do not work. Yet if I let the heater blast for 15-20 mins, boom, everything works just fine. I work second shift, and I really need some good ideas on where this fault lies before it gets alot more cold and I have to sit in my car for over an hour after work to drive home legally. I have bought a new headlight switch, but have not yet installed it. I can hear a relay clicking in the depths of the dash when I turn on the running lights, and I strongly suspect that part. I have replaced the wiring bundle that runs to the rear running lights and liscence plate light in the trunk in hope of making an easy fix on a common short (the group of wires for the lights that has to move with the trunk opening and closing). No fix there. When the lights do finally come on, they work properly - until the car sits and gets cold again. They do not flash, or go out when I hit bumps in the road, or if I jiggle that mentioned wiring bundle in the trunk. Although I have had them come ON when I was impatient go get home and just drove the car. Same deal there as well - when they work, they work until the cabin gets cold. Please help! I am getting tired of sitting in the parking lot of my work for 20-45 mins wasting fuel and time just so I can avoid a ticket. I am also planning on installing a remote start/alarm unit on the vehicle soon as well, so I really need this issue put to bed. I thank you all in advance, and eagerly await your wisdom on this head-scratcher. Majorth brijahr@yahoo.com