Major Electrical Problems

I just bought a 1997 grand prix gtp. I have noticed a few things wrong with the electrical that I didn't notice while test driving it. Well actually a lot of things.
1. First the Auto lights only work if the AC/heater blower is off or on 5. 1-4 turns them off and they don't work. Strange thing is they all work if the ignition is in the on position without the engine running.
2. The control panel only works half the time. When it does it only last a little while or is very dim. (This one I did notice but I figured it would be an easy fix so I didn't really care.)
3. The rear window defroster is not working at all.

Finally this one isn't Possibly isn't electrical
I got a cylinder 3 misfire trouble code change the spark plugs and checked for spark. Didn't work but while I was replacing the spark plugs I noticed that the number 3 cylinder spark plug looked as if it was brand new the others didn't so I'm now thinking that it might be a fuel problem. Just curious what you guy's think.

So thank you in advance for any ideas that you have.

I would check the grounds on the car. I would also remove the cluster and check its connections. Possibly some bulbs are burned out in it?
The rear defrost seems like it is an issue by itself. Check fuses, switch and then connections on the glass. If all is good, there is a short, that must be diagnosed.
For the spark plug, not sure, never had that happen to me but I would start with that cylinders coil. I would also get it scanned to try and pinpoint the misfire better.

I'm in complete agreement on the grounds. Also check the ground connection at the main ground on the transmission casing stud.

The plug, someone was trying to fix an issue with #3. Swap the wires on the top coil, between it's two posts. See if the issue occurs on #6 when you swap them. If so, it's a coil issue. How old do the wires look?

I have a 97 gt and i had the same problem.It sounds crazy but i was told to change the ignition out and it actually fixed the problem.I tried the blower control unit,Resistor,and the blower motor before i found that one out.I hope this helps.Good luck!

check the fuses. make sure none are missing. i had friend whose girlfriend's car got stollen and then pulled a fuse to make the lights shut off and it screwed up the lighting until he found the fuse wasnt there at all.

check the coil terminals and use good wires..personally when i start having misfires, iiiiiiiiiii go to my local exxon and fill up w/their 93. some of these jetpeps will make my car develop a misfire code 300.