a73sarge

I looked around before I ask but couldnt find what Im looking for. My tach moves but only about 2 or 3 lines on the dial when reved up, at idle it shows nothing. I checked the wires to see if anything was corroded or not connected correctly. Is this a common thing and the tach is just bad? Also the buzzer wont stop I checked all fluids I know of and everything seems to be ok. Its an 85 with 12a carb engine 5spd with a/c 100% factory no mods 32k mi Any ideas?