Horn fuse keeps blowing . dome lite does not work. on a 1991 chevy blazer. theres a dead short

the fuse blows because somewhere after the fuse , the wire is dead shorting out to ground
check / replace any horn relays

use a multimeter set on ohms resistance and that will tell you that it is shorting out as it will register as a circuit

My guess would be a short in the wiring for any of the components.
It may be tough to find if there are several different circuits to test.

I would recommend looking closely at your illumination circuit. There is a gray wire that if shorted could prevent the digital guages from displaying. I would look at the radio connections, especially if you have an aftermarket radio. Also, look around the lighter and maybe a bad dimmer switch.
To trace the problem with the horn fuse, look for shorts in the orange wire. Common places are around the radio or the screws that secure the panels under the dash (floor lights on the dome circuit).
As far as the no start, sound like old and dirty terminals and/or cables.

i have a similar problem but mine is my when i switch my int lights on inside the truck they blow a fuse but will work fine when you open the doors ???

You will have to trace the wiring. There is a short somewhere before it reaches the actual horn or light. Horns pull an extreme amount of amperage. The relay may be stuck or the wiring to the switch may be bad. My bet would be a shorted switch or relay.

that means you have a dead short, remove dome lite asembly and disconect, then place a new fuse... did not blow, ok you need a new dome lite assembly good luck

sounds like you have a short to ground. without more information its hard to say what it is. Are there anything else that stop working when the dome light goes out. you can also check what else use that fuse that may be the culprit

Check inside the drivers and passenger side door jam for the little push in type switch. 9x out of 10 one or the other will be causing the short to the dome fuse. These little **** get rusty and also get alot of wear and tear from the door opening and shutting over and over. These switchs are what causes your dome light to come on when you open your door and or likewise they shut your dome light off when you shut you door. A very good way to test to see if one of these little switchs is the couprate is to take and hook up a voltage light into the negative side battery post after you disconnect the battery negative line.. If your voltage light is on than that would mean that you have a short somewhere in your system. Now, since you already know that you are blowing the dome fuse then your already halfway there. With the light on your votage light still on indicatin a short, unscrew the little switch on the door jam and disconnect the power wire from it. Check to see if the light on your voltage light is still indicating a short, if not then you can be sure that the door jam was the coulprete. Hope this is of help.

it may not be a dead short turn everything connected to that fuse off and try it again hope this might help the sparking can just mean its drawing a large current

the problem could possible be a dead short in the wireing, or in the radio its self