when car is hot from setting in the hot sun all day the electrical system dose not work. any ideas?

I would not think that the car was hot enough to prevent the car from starting but your the judge. Clean and tighten the battery connections as a first step. When you say the electrical system does not work, do you mean that nothing works as if the battery was disconnected?

no...the car will start but the dash nothing come on no odometer or any thing else, no A/C, but then after a while everything is working. In the morning everything works fine.

That's completely different. The thing that is common to the different systems in the dash is the ground connection. The big "but" in that thinking is why doesn't it fail when driving around? It's unlikely that the power is being lost to all the different circuits at the same time from excessive heat...

could be something to do with an exposed wire thats getting to hot form sunlight. take it and have it looked at.

At 18 years old , I would look for corrosion or wear. Underhood, check battery, connections, cables, replace anything questionable. Under dash, examine any electrical after market modifications. Fuses, and breakers inside and underhood can oxidize/ loosen, clean/replace as necessary. Worn ignition switch contacts can cause intermittent accessory problems. A complete electrical diagnostic may be required. I know of a PT cruiser that has windows/sunroof open and close at random, as well as lights and accessories, as if posessed.