Frusterated with new tach!!!

[ts71281]

Hey gang,

Hoping someone in here has done this before. I recently bought an instrument cluster from a board member that was supposed to be brand new But that's another story. The camaro guage in the cluster appeared to be in new or like new shape unlike some of the other guages but once again, that's a whole different story. Here's my question. There's a red wire and a brown wire coming out of the back of the cluster from the camaro tach. I hooked the brown wire up to the negative side of my coil and the red wire had a plug on it that fit down in my fuse block inside the truck. At idle the tach only reads 400 rpm's and when at 60 mph the tach only reads 2200 rpm's and with another tach that's known to be good is hooked up it reads 3000 rpm's. I trust the known good tach before this camaro one. What's interesting is the fact when I get on it hard out on the highway the tach needle shoots up to 7 grand so fast it's crazy and the engine isn't anywhere higher than 5500 rpm's according to the known good tach. Then after letting off the gas the tach needle sticks around 3500rpm's and doesn't come back down until the engine comes back to an idle. then it falls back to 400 RPM's. What does this sound like to you guys? Stuck tach needle? Missing ground? I'm lost here. Any info on these camaro tach setups would be great or did I just get screwed out of a $350 isntrument cluster??? I'm getting more upset everyday over this piece. Hopefully you guys can help me remedy my problem. Thanks ahead of time for any info!

Joe Hirdler