im working on a friends 85 iroc and we are installing a air to fuel ratio gauge the gauge has 3 wires on the back a red black and green then a black wire with a plastic connecot on the end. i figured the the red is power the black is ground and the green is the acc wire that turns the gauge on when starting. where do i hook the black wire with the plastic connector on the end to? do i hook it to the co2 sensor? if so how? the car is carbed and has no computer in it at all.. please help its getting dark and need to finish

update.. ok i hooked up the red wire to power the black to ground and the gauge lit up. i touched the green wire and the gauge started to move ( other lights light up in a circle) could actually control the gauge by how hard we touched the green wire. i then tryed to hook this wire directly to the o2 sensor and started the car. the gauge started going nuts flashing from rich to lean back and forth but not reading a steady reading. the black wire with the plastic connector on the end was left alone. does this have something to do with it not reading a steady reading? or is the grean wire not supposed to be connected to the o2 sensor?

Unless you are running a Wide Band O2 sensor you will have the "sweeping effect".

ok good to know thanks.. will tell him to pick one up