how do u install a a/f meter from auto meter on a n/a 1990 fc it come black wire red wire purple wire? any help is appreciated

 

Black wire= ground

Red wire= fused power

purple wire= signal from O2 sensor

 

i connected all wires as indicated does but i still no sweep can the stock o2 be damaged, is the guage supposed to power up only on power and ground or does it need the o2 signal to light up

 

your o2 sensor prolly is bad and you should replace it
and yea the gauge should light up with power and ground so either your gauge is bad or you connected them to the wrong sources

 

Where did you make your connections to power, ground and O2?

 

i connected the red to a power distribution block made foe car stereo equip as i have my volt and oil preesure hooked up to it to. the ground is connected to a sanded down ground point under the dash and since the rx7 only has one 02 sensor wire i spliced it into that

 

did you splice into that under the hood, or at the ECU?

 

If you spliced into the O2 sensor wire at the ECU, keep in mind that it's shielded and you probably just connected to the shield (and in the process shorted the shield to the signal wire in the middle). The wire is only unshilded for a few inches at the sensor itself.

 

i connected it dirrectly to to ire from the 02 before the plug that goes into the main harness

 

Sensor side or ECU side?

Can you post a picture?

The A/F gauge is just a high impedance 1V voltmeter, so in theory you could test it outside of the car by giving it 12V and then a 0-1V source. Or connect up a spare O2 sensor in open air and heat it with a propane torch.