Tachometer - Help!
 

My 1996 Altima, with a 2389cc 16 valve, 4 cylinder engine, tach only works when it decides to. It worked fine until March and then I looked down and it was on 6. The engine was not racing, and it appeared to climb when I hit the brakes. When I turn on the car sometimes it stays a 0 for a while and then starts climbing, other times it jumps right to 2 and then other times it works correctly. I thought that it might have something to do with the temp outside as it seems to work more in the mornings than in the afternoon. I have checked the fuses and the cables, what should I look at next?