Tachometer wont work
 

My wifes car, A 96 Nissan Altima runs fine but the Tachometer doesnt work. well sometimes when its cool outside it works breifly. I've looked in Chiltons and it says nothing. What should i look at, a broke cable, a sensor, the computer, What? I'm desperate, she bitches daily like i can wave a magic wand and fix it. PLEASE HELP. Thanks