electrical issue please any help

[mikey9085]

ok so here is most of the info on the car, 94 300zx na at, when car was purchased it had an after market stereo(originally had bose system) everything was working properly, ac(auto ac control unit), lights exterior and interior, the only thing that didn't work was the speedo, odometer, and steering was stiff but pump was making noise so didn't think it was a big issue. i haven't done much to this car so far. first thing done to this i put in a little bit of a better stereo, when i dug into that project i found that the wiring behind the hu had been massacred i cut it back to the original wiring coming from harness, once i wired in stereo there were 4 wires not connected and could not figure out what there for. stereo worked but my dash lights didn't as well as my roof light, then noticed my ac panel was dim and only blew out of vents, i can adjust the temp but actual temp doesn't change only hot or cool air. kept looking through wiring to find shorts but nothing, now in the engine compartment fuse box i keep blowing fuses my ignition fuse and my power window i keep replacing fuses $$$$$, while replacing these fuses one day the steering became very easy and hasn't become stiff again . i keep searching through the fsm but i have no idea were to start some ideas would be great, i can give more info if need just let me know, also i have heard the the time control unit can cause some of these problems but I'm not positive will be checking that out tomorrow

[DCaff300ZX]

Welcome to Nico!
Unfortunately, you have made a bad situation worse with trying to wire in the stereo into a hackjob without fixing the hackjob first. With in-series wiring as you've found, other systems are affected by faulty wiring and the ONLY way is to return things to correct OEM configuration and THEN correctly wire in the stereo. I'm not an electrical guy by any means and therefore default to safe known ways to deal with electrical issues and so continuing a problematic situation such as the hacked wiring is a bad idea, and you need to reverse that.
I'd try removing the current stereo and re-attaching as much of the wiring as possible by color, and help from the OSM wiring diagrams...I know, those things blow me away, too.
If that fails I think the only solution I'd consider would be an electrical specialist who could repair the damaged areas correctly and also wire your new stereo in correctly.

[evildky]

Chances are you grounded to the illumination circuit, I've seen this a thousand times. Pull the headunit out, cut the ground wire, and run a new ground from the stereo to the actual chassis. My money says this fixes your illumination issues. As for the rest, I'd start by running new constant and switched power from other sources and see if it clears up any of the other issues.