Blowing #4 Fuse in Cab

[PSDfreak]

I was driving along today, in the truck about 5 minutes when all a sudden #4 (15A) fuse in the cab fuse box blew (Tail Lights and All dash lights went dead) I got to my friends house and checked it out finding the bad fuse. I didn't have a spare 15A fuse with me so I put a 30A in to make the 5 minute drive to my house where I had a 15A. Put the new fuse in, started the truck and as soon as I pulled the headlights knob out, POP! Lights go out...blew the 30A'er.

#4 protects the following:
-Exterior Lamps
-Instrument Illumination
-Trailer Exterior Lamp Relay
-Warning Buzzer Chime Module

Any ideas of what might cause this? One wierd thing that I noticed...If I pull the headlight knob out and hold in IN BETWEEN the parking lights and headlights setting, I can hear a click like a relay click...the headlights go out and the dash lights up, but as soon as I pull it all the way out, headlights come on, dash goes out...

I am really at loss guys...any help is MUCH appreciated!

Thanks,
Casey

 

[hheynow]

-Trailer Exterior Lamp Relay

Are you SURE you fixed your trailer wiring?

 

[PSDfreak]

I havn't really "done" anything with the trailer wiring. I had a flat four pin extension plugged into the flat four harness plug (on the truck) that I used to hook up the lights for my boat trailer...I always just left it kind of tied up under the truck. I unplugged the extension then replaced that fuse that was popping under the hood. (#5 if I recall). After unplugging it, I replaced that #5 with a fresh fuse, and it has been good ever sinse. Now fastforward to tonight...#4 fuse INSIDE the cab is blowing...do you think ALL of a sudden it would be blowing that #4 due to some problem with the other fuse/harness issue? For some reason I have a direct ground somewhere it seems (i;m guessing) which is why it is IMMEDIATELY blowing that #4 when I turn the lights on??? I'm baffled, don't know where to start

Is it possible that the "Trailer Exterior Lamp Relay" could be messed up causing the direct ground??? Where would that be located?? I know I am kind of grasping at straws here....

Thanks,
Casey

 

[PSDfreak]

Thanks for the advice guys...i got it figured out...

Tore the dash apart on the driver side and started poking around...headlight switch/wiring looked good...My neighbor who has a 1992 F-250 IDI was driving by and asked what I was doing, told me him what was up and he told me that he had a spare headlight switch in his garage I could try...popped the new one in just to be sure...no different...

Started tracing and checking other wires...marker light wires/harness for front markers looked good, bulbs worked...check rear trailer wiring/harness...also looked good....so I was stumped....called Tim Miller to get a second opinion...told me to unplug the tail lights (there is a plug near the trailer light harness in the behind the rear bumper that TEEs off to either tail light, unplugged it, reaplaced the fuse and pulled the headlight switch on...BINGO! Fuse didn't blow! I now had the problem isolated to a small area...to start I check the tail light bulbs, they looked good visually but figured I would replace them anyway just in case....got two new bulbs in, pluged the taillights back in, turned on the lights, NO BLOWN FUSE!! Whoopie! lol...All that and it was a darn bulb...

Thanks again for the help...Very relieved it was a bulb rather than a burnt wire hidden somewhere...

-Casey