Fun With wiring

Hay Gents & ladies I've got 3 electrical problems in my 1988 GMC suburban

1.Horn fuse Keeps blowing I think its the horn relay? I hooked up the fuse and it sounded is if a small motor was Moving into a set position like a cd player.
hit the horn and it worked only one horn hit it again and both horns hit it again one horn maybe a bad horn but about an hour later the fuse was blown.I replaced the fuse and no motor sound but minor sparks Maybe bad horns?
.
2.My dome lights are backwards if I use a test light and put it across the dome light terminals(holder) and shut the door the dome light comes on with the doors open and turn head light switch to dome it turns on??? like I said fun stuff

3. My fuel gauge doesn't work the guy I bought this from Didn't take care of it very well.
He replaced the fuel pump and the gauge quit working, I'm probably going to drop to drop the tank and check the wiring,electric fuel pump, when its lower on fuel,
also it has an after market stereo cd player using factory wiring old owner installed it

every thing else works fine except intermittent wipers.

after I put in a new rear end and brakes and left park cable front hubs and tires. I'm still ahead only payed $500

Part of the cure
I was suspicious of the stereo.
I checked the wiring every thing was wired to the OEM wiring except the battery back up wire.
it was wired to a red wire coming from the steering harness I cut this wire and ran a hot from the terminal block on the fire wall in the engine compartment.
A low and behold the lighter and horn work the dome lights work right.
I'm assuming until further notice it was shorting through the stereo memory back up.
Now for the fuel gauge, tomorrow


as one of my instructors use to say, ' if all else fails go back to the basics + is + and - is - every thing else is where the engineers screw things up!
dang the 70's and 80's were tough on mechanics

Your instructor was a wise man..

The first thing I did was to rip out all the creative wiring that had been done over the years, returing the dash harness back to where the factory had it installed. ( Cleaning connectors, sockets and checking grounds all along the way )

I never had any electrical problems after that effort...

dv

I have to agree the first thing is make sure that (Cleaning connectors, sockets and checking Grounds to make sure there all good all the way mount point). A lot of parts start to go bad because of bad grounds, but if they’re caught before too long they can be saved and work for a long time.

Your dome light almost sound like one of your + is grounding out and or the ground is bad and the electrical is trying to use the + as a ground point. With the dome light there is a few + jumper running off to other lights.