I've just installed an air/fuel gauge & it's not working properly - the needle keeps fluctuating from zero to half way, regardless of throttle position - have I connected it to the wrong wire on the Lambda sensor?

I've put the signal wire onto pin 1 of the super seal connector - the black wire, is this correct?

If so I take it the gauge could be faulty

http://homepage.ntlworld.com/sinister/coupe/PDF/fitting%20the%20air-fuel%20ratio%20meter.pdf has fitting instructions, have you read them?

Mmm looks like it is the right wire then (black) and my ground is straight off the battery, looks like a duff gauge then

The link above says that the signal wire from the lambda sensor is purple - not black. Black is the earth wire.

Do you have a wideband lambda sensor, or a narrow band lambda sensor?

I suspect only the standard narrow band sensor, as the voltage swings from about 0.04 volts/0.5 volts/0.94 volts over a range of something like to 13.8 AFR/14.5 AFR/15.2 AFR.

So, I suspect your gauge is working as it was designed to, but the voltage it is seeing prevents it displaying the useful detailed information you would like to see.

If you read the link, it also states:

"At idle or partial throttle the gauge shows fuelling flicking between lean and slightly rich every second or so, showing that the lambda sensor is doing it's job correctly. At wide open throttle it shows slightly rich, again as expected. The gauge does tend to flash a lot, which is kinda distracting, so the position hidden"

The purple signal wire was on the specific gauge itself, not the ECU/lambda sensor side... the sensor wire is the black wire under the bonnet.

It may just be that the AFR gauge isn't compatible with the coupe's lambda output (I wasn't aware that different sensors had different voltage outputs but apparently they do). The first type of AFR gauge I got didn't show reasonable values at all, but the one shown in the fitting guide worked fine.

That's probably the case then - not compatible, was only a cheap one anyway, not sure what band the lambda sensor is

The car uses a narrow band
I paid almost £140 for an AEM Uego (wideband) one year ago.

This was only about £20 lol, just a 'tester' but all the wiring & pod is fitted now now so easy to change it.

Ill post in the wanted section, don't want to spend much though, ill certainly never pay £120 for a single gauge lol

I think that price includes both gauge and a wideband Lambda sensor?

Then again if my sensor is narrowband - and the gauge isn't working correctly, what does that mean? As like I said it was only a cheap one

It just 'fluctuates' continuously between lean & half way, goes to rich under a acceleration.

That may be working OK, although I'd expect it to continually bounce between lean and rich at idle. If it maintains rich under acceleration it's probably working OK.

Well I suppose it's telling you the sensor is working as it should! That's about all it's useful for then by the look of it

The autometer one I had in my old coupe was accurate enough (on the standard narrow band lambda sensor) to show the difference in fuelling between different chips at full throttle, so although it may not be absolutely accurate it's fine for showing relative changes which is still very useful for keeping an eye on things.

Compare it to the "narrow band" oil pressure gauge (which only shows upto 3 bar, while the oil pressure can go much higher than that)... it's still very useful in diagnosing problems.