Fuses are the SINGLE MOST IMPORTANT part of your electrical system. They are your "protection" against shorts. They are a weak point in your electical system that will "burn out" before the wire. If there aren't fuses on EVERY part of your electrical system, you're asking for trouble. What will happen is, that something can cause an unusually high load on your electrical system. (bass hitting, rat chewing through wire, wires rubbing together and causing insulation to rub off-VERY COMMON!!!!!) When the current through the wire exceeds its capacity, the wire begins to heat up, which causes more resistance, which causes more heat, etc.... The wire then reaches VERY HIGH temps. High enough to melt, and even burn the insulation. This causes a fire. And in case you've never seen a vehicle burn, they catch on fire VERY easily and burn VERY quickly. If you want to know what will happen first hand, get a small piece of insulated wire, and short it across the poles of your battery. (don't hold it with your hand). I gurarantee that it will completely melt the insulation in a second or 2. it will catch on fire or melt the metal wire shortly thereafter.

Sound systems are notorious for setting cars on fire. The wires rub together while riding down the road, or when the bass hits, and eventually the insulation wears off. 80-90% of our fires in our county are car fires. And most of them are caused by people's stupid wiring. So fuse EVERYTHING!!!!!! If you have ANYTHING that isn't fused, its a fire hazard.
You'll also notice that almost every wire on your truck's factory system is covered with conduit, and anchored to something. This is to keep them from rubbing.

 

Gotcha, Carquest - No Mega Fuses in stock..Auto Zone had one . Murreys had the other. So, I have them . Doin it up later today , along with replacing my heater core lines. It's wet down by the knock sensor again %#@$% . I going to to fab a one piece line under the plenum - that's the second time that things leaked - if it even is , I dunno for sure yet - bet it's wet down there..

 

I put the MEGA's back in yeterday -

 

Good. None of us wanted to see your house burning on tv!

 

I wasn't worried about the house that much - That can burn -

My F150 is my main concern lol..

Thanx for the help Chester..

 

my truck right now f150 2003. I replaced the fuel pump because it wouldn't start. Replaced it and it fired right up. Drive it most of the next day,than going down the road it shut off. Now when I turn the key on the gauges for fuel wont go up and I got dots on my odometer. I wait about 30 seconds my gauges go up still no odometer, just dots. Truck wont start up. I checked the fuses,pcm relay. What could it be I'm lost.it wont show a code either. I replaced the crank sensor also. Theft light blinks 20 times than stops

 

The 2003 doesn't use those maxi fuses. Instead of hijacking a 12 year old thread that doesn't apply to your truck, please start a new thread in either the 1997-2003 truck forum or the Electrical forum. Thank you.