Just picked up a 89 Iroc Z with the 350, the door locks, hatch release switch, dome light, rear defroster and power mirrors don’t work, when I looked under the dash I found that it was missing the 20 Amp ACC fuse, I put one in just too see if it popped and it did, I’m not very good with wiring so I’m out of my element any help would be greatly appreciated, looking underneath the dash I found that the relay for the after market hatch defroster had three wires coming out of it, one ground, one to the hatch and one wire that has one of those cylindrical fuses on it, the one with the fuse isn’t connected to anything and I cant find anywhere that it would go, next too it closer to the fire wall by the kick panel is a purple and white wire with a connector that isn’t connected to anything and I can’t find anything it would connect to either, really lost and don’t know what to do

 

Below shows the Power-Distribution for the 1989 (1G1F Car) 20A Power-Acc. Circuit:

 

With ONLY Factory Information to rely on (the Schematic above that I Posted)... I always recommend disconnecting aftermarket Circuits first.
Then examine the OEM Circuits from the Schematic.

IMO a Defroster Grid should never have been installed/ powered by a 20A fuse with multiple Circuits already.

 

If the aftermarket defroster only has three wires, one to the hatch, one to ground, and one with a fuse, and the fused wire is disconnected, it's not at all likely that is the cause of your ACC fuse blowing. Now, with that said, I will tell you what the #1 cause usually is of the ACC fuse blowing, beyond someone hacking up the wiring with aftermarket radios/alarms, and things of the sort. The cigarette lighter socket is WELL known for being troublesome here, coins, small screws, and all manners of other electrically conductive crap seem to be attracted to ending up falling in there and shorting it. First look into it and see if anything is in there that ain't supposed to be and if you find nothing, try disconnecting the wires from it and see if your short circuit has been fixed(they fail shorted sometimes if they get overheated by someone plugging in one of those small 12V air compressors into it, for example) .

 

@OrangeBird made an excellent point!

That is what I get for rushing through these things and NOT reading Posts completely.
I apologize.

Those Power-Outlets/ Cigar Lighters are less and less common now... but are a constant source of Short to Ground Faults in all Vehicles.
In addition... Kids stick things in them often as well.

If you have a Multi-Meter, there are further ways to look at those Circuits.

When Head-Rest commonly had DVD/ Screens installed (10 Years ago +)...
Kids NOTORIOUSLY shoved Coins, Credit Cards, and other objects into the DVD Slots.

GM had Millions of Dollars in false Warranty Claims for the DVD Players.
You would get a phone call 6 mounts later.
GM: "Mr. so and so, I think you will want to call your Auto Ins. Co.
Your DVD Player was not defective... you have a $2,500 Bill coming in the mail.

Mr. so and so: "WHAT DO YOU MEAN NOT WARRANTY! HTF?"

GM: "Well we found 2 of Mrs. so and so's Credit Cards, and about $3.50 (TREE FIDDY) in Coins inside the DVD Player."



Mr. so and so:

 

I’ve been losing my mind the past couple days with this, I’ve checked the cig lighter, rear defrost, door locks and mirrors and still no dice, not to toot my own horn but the car is almost perfect and it sucks that none of this stuff works, i would take it to a shop but I don’t have a shop that I really trust to leave the car

 

I would unhook everything on that 20 amp circuit...put 20amp fuse in and start connecting the plugs that you took out of the circuit one at a time and see if the 20 amp fuse blows...seems like something is grounding out...did HVAC work and that is how I would find a bad wire or grounded wire working on Heat pumps etc...you may have a frayed wire in the circuit grounding out and blowing the fuse...

 

Also some of those plugs may be hard to get to unplug...that is what I would do may take time and patience but you may find what you are looking for and fix the fuse from blowing...

 

Make certain the aftermarket accessories are disconnected (Defroster, Etc).

Look at the Image I posted in Post #2.
How many of those Power-Accessories/ Options does your Car actually have?

Can you try and borrow a Multimeter?
...or even purchase a super-inexpensive one from Harbor Freight?

Take a look at the Multimeter in the Hyperlink below:
Multimeter

 

Yep, alongside my expensive Fluke digital meters and my trusty ol Simpson 260, I keep a few of those cheap Harbor Freight meters around, they work great for what they are and at less than $10 a pop it's no big deal if one gets trashed.

My best advice for the HF meters is to throw away the carbon battery that comes with it and give it a nice fresh Energizer alkaline.....

 

That is actually GREAT to know!

I have yet to buy one of those Harbor Freight meters, but suggest them when nothing else is affordable...
I will add your recommendation for the future.

I highly value small details like this.
There really is little to no replacement for experience.

Thank you for sharing!

 

Yes indeed, I'm happy to share my experience with them. Sure they may not be accurate to lab standards like the fluke, but for banging around under the hood looking to see if 12V is there or not, and for simple resistance measurements, they're a good under $10 solution. My last suggestion is to handle the probes with care, they are made of the thinnest wire possible and are a bit fragile, but as an electronics hobbyist I have a big box full of probes from old meters and I just grabbed one that fit when I accidentally pulled the wire out of one .

 

It may be the cigar lighter, on my '92 it now resides in the console. The piece that gets pushed in was shorting out the socket and popping the fuse. It was so intermittent, took a long time to figure that one out. Actually got a 20A auto-reset breaker and installed it for a while.

Note that the socket is still good, use it to power a 120V inverter for the laptop.

RBob.