for a long time i had a 5inch autometer tach in my car. when i took it out and hooked up the original tach in the cluster it wouldnt read right. when the car is idiling the needle sits at 0 then when you are driving anr reving high it is usually about 1500 rpms off. i cant figure out why it does this. any ideas???

 

Your gauge cluster is probably faulty and its time to go get a new one. This is the factory gauge your talking about right?

 

i am talking about the factory cluster. but both of my cars have the same tach problem. only had this problem since taking out the other aftermarket tach.

 

You probably unknowingly disconnected a wire, or frayed something or what have you when you were patching into the tranny to install the aftermarket tach. Go ahead and kinda check your work to see if theres anything that looks wrong.

 

i disconnected the tach wire right from the plug that connects to the cluster. just the one tach wire, nothing else, then when i took the tach out i re-connected it.

 

hmm. must be soemthing wrong with your gauge cluster.

 

its just kinda weird. two cars two different aftermarket tachs and three different gauge clusters(i replaced one and still same problem)

 

Was the needle ever taken off the cluster? If so try removing the needle and then turn the key on and putting it back on that way the tach is at 0 to start with i had that problem and thats how i fixed it when i changed my gage face.

 

Are the aftermarket tachs installed when you are getting a lower reading on the stock gauge? Could be the aftermarket tach is pulling too much power and the stock gauge is not getting enough voltage.

 

when i hook the aftermarket and stock tach up at the same time the aftermarket one doesnt work only the stock. the gauges have never been apart, just unplugged, then if i unplug the stock one, the aftermarket works great