I just installed a a/f ratio guage. it was a simple 3 wire deal, power/ground/o2
I hooked my power through an inline fuse and directly into an ignition port in my fuse panel (power with ignition on)
it works good, or so i though, I discovered last night, that if I put my headlights on, heater, stereo etc. the readings on the guage are effected! is this normal? with everything on, the guage reads leaner than if I have all my accessories off.

so i spose I should wire my power directly to the ignition switch?

 

Common problem, wire isn't a large enough guage. My friend thought his volt gauge was broken but I showed him that it was because he wired WAY too much crap to a single power source. All you have to do is go to your battery and watch the volts, they shouldn't dip much if any when you have hazards on (that's the REAL test).
A good idea would be to run some stereo 8 gauge wire from the battery to your dash, run a small wire with it. Then install a relay next to the battery. Hookup the small wire to the ignition switch/wire. Make SURE you fuse BOTH wires.
I plan on installing a second alternator for my stereo and acc in the stock air pump location, when I do that I'm going to pretty much rewire my whole car....again.
You have to understand that these cars were built to stay stock and keep production costs low. That is why they got a small case design alternator which doesn't give many choices for upgrades, same thing goes for the t5 tranny and 10 bolt rears.
Do what you want but I would definatly try and get an uninfluenced power source for a more accurate reading. Good luck

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, Jon (350 TBI!)
91 Red My website

 

well tonight, my alt stopped charging I think, usually the volt guage stays in the middle, but with lights on and heater etc it was way down almost at 0. lights were very dim.
I had my alt tested a month ago and I was assured it was still charging strong..
so would too small guage of wire cause this prob as well?