Thanks Ogre for your informative reply.
Yeah, sorry I just meant grounding some gauges and indicator lights for now. I went and got a terminal block for connecting them all, might be overkill, but it's working good. I took your advice and picked up some dielectric grease. I used the G201 ground point you mentioned for this new ground and cleaned the metal good. (I'll put up a picture of the dash you helped me light up!
I never thought about that for the power windows, mine are very slow. I'll definitely clean the G301 ground another day and see if that helps. They are working, so maybe I'll just focus on stuff I'm in the middle of for now.
So today I was trying to figure out the parking brake circuit. I want the "Brake Indicator" wire C3-14 to put out 12 volts to power the indicator on the instrument cluster (not a Fiero cluster).
I read the circuit and located a purple wire coming out of the parking brake (see attached diagram). I followed the wire and saw it go through the two connectors and then turn to the different colour. I took my voltmeter to it between the parking brake and the first connector and got 0 volts. I took a reading on that C3-14 wire and it was .1 volts with the purple wire connected and .3 volts with the wire cut. I'm very confused.
(My "Buzzer" is currently removed as it was driving me nuts months ago, maybe I should have tried checking with that installed)
(Also there was a second larger gauge purple wire running with the smaller one, I was playing with the smaller one)