can anyone tell me how to wire up a ford aftermarket three wire oxy sensor, to a afr gauge, on the oxy sensor it has 1 blue and 2 black wires, i take it as the blue been the signal to the gauge, but what are the 2 blacks for, is one a ground and one a 12v, or both blacks are grounded to the motor or something, cheers.

If it is a three wire heated O2 sensor they are the power and ground wires for the sensor. I don't think it makes a difference which is ground and which is power, not 100% on that though. To wire the gauge you will need to tap into the sender wire and get power, ground and dash light wires hooked in to the gauge.

The 3 wire sensor has one ground connection and one heater wire. It also has the Oxy output wire as well which totals 3 wire. The Black wire is the ground and the white wire with the lowest resistance is the +12v for the heater. The other white wire is your HEGO output wire too the ECU. This is the wire that goes to the A/F gauge. For the EF/EL it is the Dark Green with Dark Blue trace.

cheers guys the oxy im using is a aftermarket one a aca ox207 it has 2 black and 1 blue so il just use the blue as the signal to the gauge and the 2 blacks il put as 1 12v and one ground see how i go with that.