99 - Fuse #11 blown, no running lights, fogs, or dash lights

[trj360]

Hey guys,

I just started having this problem today. My front and rear running lights go out along with my dash lights and my fog lights. So far I've traced the problem to the #11 fuse (15A) in the under-the-hood fuse box. A new fuse lasts maybe 10 seconds, the lights flicker/pulsate, and then the fuse blows and it all goes dark again. The main headlights, brake lights, and turn signals remain unaffected. Where should I go from here? Which relay feeds the #11 fuse? I'm also seeing similar symptoms from people with a bad headlight switch, but taking the dash out is last on my list of things I want to do. I'm looking for some input or advice before it comes to that.

Here is the thread I found regarding the #11 fuse:
http://www.explorerforum.com/forums/showthread.php?t=304446

One problem I'm having with the threads I find is that nobody comes back to update them to say what the problem actually was.

 

[koda2000]

if the fuse keeps blowing you have a short in one of the circuits protected by fuse #11 . try keeping the fog lights turned off and the dash lights turned off. that will at least eliminate them from the problem. it's a bit odd that the fuse doesn't blow immediately. this could indicate a poor connection or ground.

question: does your truck have trailer light wiring? if so, start by checking these wires for bare spots. i have found that improperly/poorly installed trailer light wiring often causes problems.

 

[trj360]

I left the truck sitting with no fuse in the 11 spot overnight. Went out this morning, threw a new fuse in it with the fog light switch turned off. After turning the headlights and running lights on, nothing blew. I was feeling confident that it was the fog light switch, since turning it off was all I did differently, but then I turned the fog lights back on and the fuse still didn't blow. I sat in the driveway for 15 minutes turning every switch on and off repeatedly with no problems, including the dash/instrument lights using the dimmer.

I also do have trailer wiring. After playing with the switches and buttons and having no trouble this morning, I went to the wires behind the rear bumper and wiggled them around with no issues. They do look nasty though, there are 4 wires that just have bare ends. I've never towed with this truck so I've never had a reason to really inspect them. I tried touching the ends together, to the frame, to the bumper, in the hopes of finding a short, but nothing happened.

 

[koda2000]

if you have trailer wires with bare spots or ends, if they touch anything metal it will blow a fuse. which fuse depends on which wire: tail/running lights (usually brown) brake/turn signals (usually green & yellow). the only wire which can/should have a bare end is the ground wire (usually black). if your colors are correct, the brown wire could be the one causing a short. this is the same circuit for tail & dash lights. i don't know if the fog lights are on the same fuse, but apparently they are.

if i'm understanding your last post, you're saying that with the fog lights turned off the fuse does not blow? try driving it with the fog lights OFF and see if the fuse stays good. if it's something to do with the fog lights, i doubt it's the switch. probably the wiring. check out the wiring at/around the fog lights.

if the fuse only blows sometimes you have an intermittent short somewhere. it may only blow the fuse when you turn or hit a bump, because that causes a wire to touch metal and short out.

 

[trj360]

if i'm understanding your last post, you're saying that with the fog lights turned off the fuse does not blow? try driving it with the fog lights OFF and see if the fuse stays good. if it's something to do with the fog lights, i doubt it's the switch. probably the wiring. check out the wiring at/around the fog lights.

I turned the fog light switch off before I started the truck this morning, as the first step in my process of elimination. The fuse did not blow with the switch off so I figured the problem was something in the fog light circuit. However, I turned the fog lights back on, and still, the fuse did not blow. I'll drive with them off for a few days and see what happens.

As for the trailer wires, I actually touched all 4 ends together while the truck was running and the fuse did not blow. Shouldn't that cause a problem? I can post pictures of my trailer wiring tomorrow if you're confused about what I'm saying or just curious.

 

[trj360]

Today's update:

No problems driving around with the lights on for an hour. I cleaned up the trailer wires so there shouldn't be any bare metal, although I did not dig into the plugs to see if they were messed up (not yet anyway).

I got where I was going but when I went to leave, the fuse blew again maybe 30 seconds after leaving my parking spot. I pulled into a parking lot and unplugged the fog lights. Another fuse blew after a couple seconds. Turned the dimmer switch to the off position, which turns off the dash lights, and another fuse blew. Finally I gave up and just drove home with no running lights.

Looks like either the trailer wiring is being cut out tomorrow, or the dash comes out, or both. Hopefully I can find something obvious, whatever it may be.

Edit for clarification - when I say "another fuse blew," I mean the same fuse, #11 . I'm carrying a big box of 15A fuses in the truck with me.

 

[2000StreetRod]

BJB Fuse 11

I don't have a 1999 wiring diagram but your wiring should be very similar to my 2000. Fuse 11 in the battery junction box provides the power to energize the headlamp relay, park lamp relay and dimmer relay in the relay module and also the main light switch. I don't see a way that the trailer turn signals or tail lamps could blow fuse 11. They would blow fuse 3, fuse 7 or fuse 30 in the central junction box. I also see no way that the fog lamps could blow fuse 11. My guess without spending a lot of time tracing wiring diagrams is the dimmer module. It has a pulse width modulator that receives power from fuse 11 when the park lamp relay is energized. Do you have autolamps? The park lamp relay is energized by autolamps. If you have autolamps, turn it off and see if fuse 11 still blows.

 

[trj360]

Are autolamps the automatic headlights? If so, I don't have those.

At this point, I'm thinking it's either the headlight switch or the dimmer, both of which require taking the dash out.

 

[trj360]

I took the dash panel out and got the headlight and instrument dimmer switches out. Is there any way to tell which one is bad?

 

[trj360]

My guess without spending a lot of time tracing wiring diagrams is the dimmer module. It has a pulse width modulator that receives power from fuse 11 when the park lamp relay is energized. Do you have autolamps? The park lamp relay is energized by autolamps. If you have autolamps, turn it off and see if fuse 11 still blows.

Although I don't have autolamps, I turned the interior & dash lights off and the fuse still blew yesterday. The dimmer switch I'm talking about is for the dash and not the one for headlights as I'm seeing in some other threads. Since the fuse blew with the dash/interior lights switched off, does that eliminate the dimmer switch? I hope so because that dimmer is hard to find, looks like an ebay or junkyard-only part.

 

[2000StreetRod]

dimmer PWM

Not having autolamps simplifies things a little. The park lamp relay is a single pole, double throw relay. When the relay is energized power from fuse 11 passes thru the relay contacts and is routed to the pulse width modulator (PWM) section of the dimmer module. When the park lamp relay is not energized power from the main light switch (when in park or head position) passes thru the relay contacts and is routed to the dimmer PWM. The park lamp relay is energized by the RAP module. The main light switch also gets power from fuse 11 in a round about way. So the only time power from fuse 11 is not applied to the dimmer PWM is when the main light switch is in Off and the RAP module is not activated. The dimmer module includes a switch for the interior courtesy lights but not for the instrument lights. The instrument lights are always controlled by the output of the dimmer PWM.

Power from fuse 11 is also routed to the GEM when the light switch is in Park or Head. I guess there's a possibility there could be a short in the GEM.

Fuse 11 also provides the energizing power source for the headlamp relay, the park lamp relay and the dimmer relay. There's a possibility any one of those solenoids could be shorted but that's an uncommon failure mode for a relay. And usually if a solenoid shorts the fuse would blow immediately.

 

[Robman]

I have had much the same problem before, The Daytime Running light module likes to die on these it's located in a poor spot, gets wet and abused, ahead of the drivers side front tire. When this malfunctions you will get fuse blowing problems or other high strangeness, or you have a bulb that is about to die and drawing too much amperage. OR you have a bad multifunction switch or other wiring problem. My guess is the DRL module. My 2 cents, could be wrong.

 

[trj360]

Not having autolamps simplifies things a little. The park lamp relay is a single pole, double throw relay. When the relay is energized power from fuse 11 passes thru the relay contacts and is routed to the pulse width modulator (PWM) section of the dimmer module. When the park lamp relay is not energized power from the main light switch (when in park or head position) passes thru the relay contacts and is routed to the dimmer PWM. The park lamp relay is energized by the RAP module. The main light switch also gets power from fuse 11 in a round about way. So the only time power from fuse 11 is not applied to the dimmer PWM is when the main light switch is in Off and the RAP module is not activated. The dimmer module includes a switch for the interior courtesy lights but not for the instrument lights. The instrument lights are always controlled by the output of the dimmer PWM.

Power from fuse 11 is also routed to the GEM when the light switch is in Park or Head. I guess there's a possibility there could be a short in the GEM.

Fuse 11 also provides the energizing power source for the headlamp relay, the park lamp relay and the dimmer relay. There's a possibility any one of those solenoids could be shorted but that's an uncommon failure mode for a relay. And usually if a solenoid shorts the fuse would blow immediately.

Thanks for the information - I'm not much of an electrical guy so what I think you're saying is that it's probably the instrument dimmer switch? For what it's worth, the instrument dimmer works just fine for the few seconds fuse 11 doesn't blow. I can turn the interior lights on and off, and I can dim or brighten the dash as normal, but like I said only for a few seconds, maybe less. I've gone through something like 6 fuses troubleshooting so far.

I have had much the same problem before, The Daytime Running light module likes to die on these it's located in a poor spot, gets wet and abused, ahead of the drivers side front tire. When this malfunctions you will get fuse blowing problems or other high strangeness, or you have a bulb that is about to die and drawing too much amperage. OR you have a bad multifunction switch or other wiring problem. My guess is the DRL module. My 2 cents, could be wrong.

Daytime running lights are the same as autolamps, right? I don't have those. My lights are totally off until I turn them on with the headlight switch.

 

[kenfz6]

While troubleshooting, have you thought about replacing the fuse with a circiut breaker? Only need to buy one.

http://www.amazon.com/Bussmann-BP-U...392034672&sr=1-6&keywords=15a+circuit+breaker

If the breaker doesn't fit, use pigtails to get it into the fuse holder.

 

[2000StreetRod]

Autolamps vs DRL

Autolamps automatically turns on the headlamps, exterior lamps, and instrument illumination when ambient light level decreases to a preset amount. Daytime running lamps (DRL) illuminates the low beam headlamps with pulsed voltage for reduced brightness and increased longevity during daylight conditions. It's mainly a safety feature. I see no way that DRL could affect fuse 11.

You might try disconnecting the GEM and see how long the fuse lasts. They are known to sometimes fail in a shorted mode.

 

[trj360]

I don't have any of that. My headlights are either on or off, they don't ever come on by themselves. When I said "running lights" in previous posts and the title of the thread, I meant the parking lights, the middle position on the headlight knob.

How would I go about troubleshooting the headlight switch or the dimmer switch, short of replacing them?

Can I plug the headlight switch back in, leave the dimmer out, and run the truck to see if the fuse still blows? Would that work or would the missing switch cause other problems?

 

[2000StreetRod]

headlamp switch

The headlamp switch is a three pole, three position switch. One pole is for the headlamps and the other two poles are for instrument illumination. Installing the headlamp switch and leaving out the dimmer module will provided headlamp high and low beams, fog lamps and I think parking/exterior lamps. You may not have courtesy lamps or instrument lighting.

 

[trj360]

The headlamp switch is a three pole, three position switch. One pole is for the headlamps and the other two poles are for instrument illumination. Installing the headlamp switch and leaving out the dimmer module will provided headlamp high and low beams, fog lamps and I think parking/exterior lamps. You may not have courtesy lamps or instrument lighting.

Right, so in theory it should work like this - If the dimmer switch is at fault and I start the truck without it, my parking lights should stay on and fuse 11 should not blow. If the dimmer switch is not at fault, the fuse will still blow with the switch removed.

The dash lights go out with the parking lights so I only need to see one of the two to quickly tell if the fuse has blown.

 

[trj360]

If this diagram is accurate (says 95-97, autozone says up to 99), it looks like there is 1 wire from the headlight switch and 1 wire from the dimmer switch going to fuse #11 . This doesn't really help me all that much because I'm not really sure what I'm doing but it's a nice illustration. All this does for me is confirm that it could be either switch, or some random short somewhere.

http://repairguide.autozone.com/zne...96b43f/80/21/b9/8f/large/0996b43f8021b98f.gif

 

[2000StreetRod]

Not complete

The diagram doesn't show the dimmer module for the instruments or the dimmer relay. The headlamp circuit looks accurate. The dimmer switch shown is for high/low beams not instrument light dimming.