Weird electrical problem.

I currently own a 89 integra ls that I have been driving for 3 or 4 months. Since I bought it, it has had a electrical problem around the instrument cluster. For some reason, whenever my car is hot the tach, e-brake light, lights behind the climate control, and a couple other things do not work. However, if it is somewhat cool out, all of them kick in. When the kick in though, the oil light flashes. As soon as I turn the car off however and turn it back on, the oil light stops flashing but everything else still works.

If any of you could clue me in on why certain things don't work when its hot out, it would be greatly appreciated. BTW...I am in florida so it is rarely cool here.

Probably the dimmer switch.