So I am finally trying to figure out why my rpm gauge doesn't work and I discover I can only find two wires...which makes no sense to me because their are 4 places on the back for wires. So I am just wondering if anyone has this gauge in their 914 and if they might know the answer to my wire predicament?
Here is the front
Click to view attachment
Here is the back
Click to view attachment

Unique guage. I've never seen a tach/fuel tank combo before.

If I remember correctly it's a 911 tach gauge. If I am wrong though please correct me.

With a date stamp of 3-79?
Early 911's tach connections were +12v,+6v,trigger wire,and ground.
Look closer on the plastic.
good luck.

I second the 3 wire hook up, one of the 2 center is ground and the other open.. Also second "read the plastic markings"

Ok. The writing on the plastic reads this left to right: +12 TD G -...these writings still don't help me in the fact that I only have two wires coming from the dashboard.

I have a tach just like that in my car. It's a tach from a 930, and the small gauge at the bottom was originally a boost gauge that read either 0-1.5 bar (1977 only) or 0-1 bar (1978 and later). Someone has had North Hollywood Speedometer, or someone with similar skills, re-do the face, and perhaps the movement, of the small gauge to turn it into a gas gauge. The way to hook it up is with the red/white wire going to "+12" (the connection on the original 914 tach that this wire goes to would have been labeled "15"), and with the black/red wire going to the "TD" terminal (on the 914 tach, this would have connected to a terminal labeled "1"). The "G" terminal goes to the small gas gauge movement, and the other connection is a ground. If you want to use the small gas gauge, the green wire that used to go to the gas gauge in the combination instrument should be hooked to the "G" terminal.