I have posted before and got advice cause my tach kicked the bucket. The general suggestion was replace my 84 gauge cluster with another one. Okay I got two different clusters off of e-bay one was supposed to be good the other one was thrown in for parts. Here is the thing neither tach works one goes to zero when the key is turned on but when the car starts it shoots up to 2200 and stays there till you give the car gas then it drops back to zero till you let off the pedal. The other tach shot up to 7000 and never did anything else. So I ask now what should I do????????

 

its possible that there is a wiring problem. there's only one wire that feeds the tach off the distributor. it may have intermittent contact or a bad ground.