Fuse keeps shorting out as soon one's put in

It is never as straightforward as you think because the entertainment system is monitored and run by the body control module and put warning chimes and things like the blinker clicker through the audio system.

https://www.google.com/search?q=2003+Mercury+Mountaineer+radio+and+entertainment+wiring

..

Question edited for clarity.

Fuses 4 and 8, but there is also a relay involved.

Fuse Box Diagram Mercury Mountaineer (1997-2001)

https://fuse-box.info > mercury > mercury-mountaineer...

Here you will find fuse box diagrams of Mercury Mountaineer 1997, 1998, 1999, 2000 and 2001, get information about the location of the fuse panels inside ...

Mercury Mountaineer (1997 - 2001) - fuse box diagram

https://www.autogenius.info > mercury-mountaineer-19...

Aug 11, 2018 - Mercury Mountaineer (1997 - 2001) - fuse box diagram. Year of production: 1997, 1998, 1999, 2000, 2001. Passenger compartment fuse panel.

Mountaineer » Fuse Diagram

https://knigaproavto.ru > Fuse Box Diagram > Mercury
Fuse Box Diagram Mercury Mountaineer; engine 4.0 L Cologne V6 and 5.0 L Windsor V8 (1996, 1997, 1998, 1999, 2000, 2001)

https://www.justanswer.com/mercury/6604r-mercury-mountaineer-2000-merc-mountaineer-v8-awd.html?__cf_chl_jschl_tk__=bbdbbbd251dcaf0d223c7729cef468700f284312-1611184040-0-AVeIHfZ8RmCycIou7H5xWIlsxfihqLjvVne6YZy5iuHMUahR9XlH29FV68MiYM8U9Mjy2hmzDsiiaA0h1RBOv78xXhLLd-ZuiFJG0G0-18ux6rBNpsk3N5lstNwynG8Uiwsy0bH9PuMnD3zT2OIeLuXOZBwE-AWcVoCyb2yqlGlEnYtE3EvF0jpONUAuqShMJrUQ32dYpDjVrkVc_2QbjKTeomjzDAK5QfqrAviS54lcIniLUgSXdRExtYQ4SHmQuUmsz_d-e3tPhyFJcE6Yadm5pX9J3TuMlEzAGwQOlaoc8_qB46Ire1OVA2ySQ6YOap4pHqEKF1ixo7Otuh_lId6EPm9N6tXGcBiI8ml8OBIMpzRROiQ-jXe75USAzEZtUNbF1GDjMls7tfASq5MFD8B3qxkI5xDTzm3x-RE0MMNFW281KpqWdQq3siBaqCMTP9cAgihVyZC6KNTcjUoCOqc

when the motor starts to go out it can cause mechanical resistance, causing the amperage to increase (blown fuse). Its also possible that the B+ wire has frayed causeing a short to ground which also would pop the fuse.

The fuse for the horn would be in the power distribution box located under the hood in the engine compartment (see picture below). Also below is a diagram of the fuse layout. The fuse you want to check will be the fuse in the number 10 position and should be a 15 amp fuse. There is a horn relay as well and the is the relay in that same box in the number 7 position. I hope this helps and good luck.

following the fuse diagram of mountaineer

Fuses would be the first suspect. Look for a small bread-loaf size box that contains all the fuses and relays. If a new fuse pops as soon as a seat or lock is operated, then look for a stuck motor for the seat or a shorted solenoid for a lock that was just operated. If it pops as soon as replaced, then suspect a wiring short.

you have a loose wire grounding out and your fuse will keep poping till you find that grounding point !! check all the appropriate connections and harnesses. I hope this helps good luck

Disconnect as many of the door switch wiring plugs, and wiring plugs for the seats that you can. Then, drop in a fuse. If it blows, you probably have a wiring issue, not a switch issue. If it doesn't blow immediately, reconnect the doors, and seats one at a time till the fuse does blow. Once it does, you've isolated your problem to a smaller area, and can replace / rewire that component.

If you've disconnected everything, and the fuse still blows, you probably have a wiring issue that will need to be traced. You will need a multimeter that can read ohms. You'll need to isolate different parts of the circuit (probably by unplugging and or cutting a wire in that circuit unfortunately) then use the multimeter to test the ohms from that part of the circuit to NON voltage side of the fuse holder. (If you try to test ohms on a hot circuit you will likely fry your multimeter!). If the meter reads low ohms, there is your short. High ohms (infinity) means there is no circuit, and there is no short. When you hit on something of low ohms, you've isolated the problem to a smaller area, and can keep tracing that wiring back to the fuse box to find your short.

Good Luck.

This seems too bad wiring or major short in the car which is causing the fuse to blow ,change the wiring of the car .