HELP...Im trying to wire in a air fuel ratio gauge.

[DodgyDan]

Hi everyone,
i just wondered if anyone out there can help me at all,i have bought an AUTO GAUGE AFRLEDSWL-20B 2" AIR FUEL/RATIO GAUGE but i am haveing some trouble trying to find a wiring diagram or any body that knows the correct wire to chop into,from looking at the car (legacy 2.0 gt twin turbo,BG5,1994)it has 3 sensors on the exhaust system,one in the cat which looks like a temp sensor and has 2 wires,one a bit further up towards the engine on the left side of the exhaust (left side form sitting in the car)which also has 2 wires and looks like a temp sensor but then on the same side further up on the system (on the complex bendy part of the downpipe) which is a bigger sensor which looks like the correct one and this has 3 wires going to it.
On my gauge i have 3 wires,black,red and grey and in the instructions it doesnt tell you where the black and red go so i imagine that these are just the live and earth to power gauge up,it only says that the grey wire has to be connected to the O2 sensor signal. and i dont know which wire this would be on the car,can anybody please help......Thanks for reading.

[Huffer]

I recommend:

www.clubsub.org.nz (http://www.clubsub.org.nz)

for this type of specific question. Plenty of BG TT owners there.

[DodgyDan]

Cheers Huffer,Will give them a try.

[Legacy4Life]

I had wired an AF Ratio meter in mine before it got stolen. Two of the wires on the meter are for 12V and Ground, the other taps into the O2 sensor.

My car uses 3-wire O2 sensors as well. They are better than 1-wire sensors because they are self heated. I think that on most O2 sensors, Black is the signal wire. You could always test the wiring once the engine is warm by using a DVM. Your signal wire will only be between 0 - 1 Volt DC and will fluctuate quite quickly between 0.2 and 0.7 when working properly. It never stays still. One of the wires will always be at 12 Volts, the other will either be for sensor temp feedback or ground.

Don't know if that helps or not.

[DodgyDan]

Thanks ever so much Legacy4Life i will give it a go this weekend when i have a bit pf spare time.every bit of info is a help,Cheers Mate