Hi,

I hope someone can help me because I just keep getting more frustrated. I have a 1998 F-150. Fuse #7 under the hood keeps blowing causing my tail lights and instrument panel lights to go out. Any suggestions?

 

Does the fuse blow when you plug it in, or can you cause the fuse to blow by depressing the brake pedal ect.

 

Is it safe to assume that fuse 7 is for the tail lights ?

I looked in my 2001 SCrew manual, and Fuse #7 under the hood is the horn fuse.
Next I'd have the same question, does the fuse blow when you put it in, or do you have to turn the switch to the parking lamp position to blocw the fuse ?

Also additional question, do you have any additional items on the parking light circuit ( i.e. a switch for the relay power for after market driving lamps, running bd lamps, neon, etc ).

Just a few more questions, sorry I could not find a fuse location chart straigth away for your year truck to verify the fuse position, to make sure we are taling the same thing.

 

It doesn't blow right away. I will change the fuse and then turn on the lights and then it blows. Nothing else is hooked up to the fuse.

 

Both scully and I show #7 fuse as the horn in our books but you have a 1998.

I assume by "lights" you mean headlights and if so, you have a short somewhere in that part of the wiring that you need to troubleshoot.

 

With nothing else attached to the parking lamps, I guess the next step is to trace out the wiring harness in the front by the parting lamps, and in the rear by the tail lights.

These are some quick start points, hoping that it is not a skinned wire behind the instrument panel.

If it takes turning the parking lamps on to blow the fuse, then my next guess is a chaffed harness somewhere along the "output" side of the parking lamp switch. That is a lot of wiring to trace out, but it looks like you are going to have to take the dive and trace the majority of it.

My method would be to take out the front parking lamp buckets, and the tail lights, and wrap dry towels arund all 4 of them and try again. This is checking to see if there is a skinned wire near the end of the circuit. The correct method would be to break the circuit in the middle, and see if it still happens, but I am sure you would not be looking forward to cutting the harness apart under the truck for this

Use your own judgement on this, but I would look to the ends of the circuit first, maybe the last time you changed a bulb, the harness got a slight pinch in it, and it just now rubbed all the way through it. ??? big SWAG at this point, just thinking outloud.

Taking out the instrument cluster, and looking at all the interior lighting is not going to be fun. This is tracing every illuminated switch, and dial the whole way through the system

Good luck, let us know what you come up with.

 

#t fuse is the Main light switch & Park lamp relay. Do you have the trailer tow option? In that same fuse box where the #7 fuse is there should be 2 little mini fuses all by themselves below the big relays. One of them is a 20 amp fuse if you have the TT option. Pull the 20 amp fuse and try the #7 fuse again.

JMC

 

More questions. When did this start? What was done to the truck prior to this happening? Oil change, power wash, light bulb change, backed into garage and hit wall, installed??? Did you hook up a trailer? Install a trailer electric brake switch?

JMC

 

It just started one day. About a month ago or so it started blowing. It would go a week or so and now as soon as you put the fuse in and turn on the lights, it blows and I have no tail lights. I am going to try the suggestions tonight. The trailer lights never worked right from the time I bought the truck.

 

If you can get the bulb numbers for the lights that quit working when the fuse blows.

I have heard that some folks put headlamps in that pull too many amps for the circuit and that the wires were sized too small. The fuse would not blow but the wires would melt the insulation. I suppose a short would occur shortly after that.

If it is not a melting wire problem, then you might have bulbs that pull more amps than the circuits are designed for.

 

this definitely sounds like a short in your wiring. good luck with finding that

 

Let me ask a question just to clarify, does it blow the fuse on the first position ( parking lamps only ) or on the second position ( parking and head lamps ) ?

Are the front parking lamps out as well as the rear and instrument ( all interior lamps ) or is it just the tail lamps ?

Just want to make sur of what I read, understood, and infered by the earlier posts.
JMC actually has a great idea I had not thought of, taking out the Tow fuses.

Good Luck let us know what happens.

 

Steve,

According to the schematics the #7 fuse protects the parking lights and the instrument panel illumination. A blown fuse should take out both front and back. If it doesn't we are in major ka ka.

JMC

 

One more question for ben31; Did you install a trailer light converter to allow you to plug into a non standard pig tail? Do you have a flare side or a style side?

JMC

 

JMC,

That is why I was asking. I was kind of assuming that this was the case, but thought better to check, less I make yet another bad assumption. I got enough of those for the month already, and it is only the 6th

Steve