so i was trying to install my boost gauge but I cant figure out where to connect the power supply. I know the black wire goes to the ground. but where do I connect the orange, red, and white wires?

 

what boost gauge do you have? mine only had a black and a red wire for the light bulb and the air hose for the boost

 

I bought a defi gauge

 

is this a mechanical or electronic boost gauge? if it's electronic (with it's own MAP sensor) like the Autometer i put in my Spirit R/T, then you will need to run the power wire to a place that has power with the key on AND while the engine is cranking.

 

I was told it was kinda a combo of both. where are those locations to wire it for power then?

 

try the fuse box its kinda ghetto but just put the wire in the fuse lead and plug the fuse in to secure the wire. but use the ignition fuse bc thats power with key on and crank.

 

sounds like you have an electronic boost gauge. my Autometer electronic boost gauge has a vacuum/boost hose that goes from a McMaster-Carr manifold distribution block (mounted on the intake manifold). this hose goes to the 3-bar MAP sensor that came with my Autometer electronic boost gauge. from there, there is just a wire harness that goes straight to the back of the gauge. there is a ground, dimming, and power light. the power light must be connected to a place that has power with the key on and while the engine is being started so the gauge can calibrate itself every time the car is started to ambient pressure (so it can "zero" itself and therefore be accurate). i have tried mechanical boost gauges and found them to be extremely inaccurate. this may be due to my high elevation however. the needle would always sit at 1-3psi with the engine not even running. the electronic Autometer is always dead on.

 

where exactly would the spot be to connect them then?

 

on an Audi, i do not know. use a voltmeter and hunt around for one on different circuits. have someone crank the engine while you check to see that power isn't dropped while cranking (and that power goes off when the key is off of course). that's probably your best bet.

 

Ignition switch and/or starter relay circuit maybe?

That's really the only temporarily energized circuit on start-up that I can think of.