99 Explorer fuse 26

[ajb999]

I've got a 99 Explorer that has a short somewhere and trying to put a fuse in #26 blows the second it touches.

My rear defrost, rear wiper, and HUD?(thing above the rearview mirror) have never worked since I bought it. I believe the drivers side door has been replaced as all the wires running from it into the vehicle have non factory connectors and it's missing the rubber cover.
Occasionally the drivers side switch for the drivers window will not go up when pushing up then go down about an inch. I've traced it back to a spliced wire I just haven't had time to fix. I don't think this is part of my problem but just giving info.

So onto the new problem. I went to work, locked my vehicle and walked inside. About 5 minutes later people are yelling for me that my car has smoke coming out of it. Got in and smelled like burnt plastic/electrical but had to work. Go out on my break and windows not working. Start checking things out and no interior lights, running lights, 4x4 lights are flashing on dash. Check my fuses and 26 is blown. Also I think 29, the one for the radio. I work swing shift so don't get off until 11pm so know at the very least I have to get the running lights working. Run get some fuses, try to put one in 26 and arcs as putting in so just put it in to make sure since I've got extra and it blows. Also replaced 29. Driving back to work the radio stayed on but when I went to leave it was blown again. Left work early so I didn't get pulled over for no running lights. Also, the previous owner had replaced the stock 10a with a 30a so problems before.

So today I started pulling stuff off the dash and the front drivers side pillar and the entire way up the bunch of wires that go to the interior lights, vanity mirror, rear defrost and wiper have a burned wire that's melted into other wires at some point. I traced it as far as I could to the dash and it was melted almost everywhere I could see. In a hurry to get to work I cut it with enough slack so I could connect them all later. I know, super stupid but I was in a hurry for work. Still the fuse blows with key out, everything I can see to turn off I did including inside lights.

I tore the dash apart today trying to figure out where the bundle of wires go and after they enter the front drivers side corner of the dash I can't find them.

I'm not sure to go from here because this is my only transportation and I drive 30 mile one way for work. Also I'm not sure why the radio fuse started blowing alongside this. When they saw my car smoking one guy said it looked like it was coming from somewhere on the drivers side.

Sorry for the long post but just trying to give as much info as possible. Any help or suggestions will be greatly appreciated. I'm not the most knowledgeable car guy but have learned a lot working on them but when it comes to electrical systems it's probably my weakest area.

 

[1998Exp]

OK, this seems like a big issue, there is obviously too much current coming from somewhere. my first though goes to resistors, and the replaced drivers door. maybe, the wiring was done improperly, so too much voltage went thru, but the fuses saved your a** by blowing instead of letting too much current through. Is the battery the right one, because if so, that could force too much power thru and cause an electrical fire. also, because they're running 30a, it needs 30a, so they might have had it run 30a, but the other parts couldn't handle it. also, do you happen to have the bin, so i can check for any recalls, because there was an electrical one i thnk. also, if you can, look for codes, because those can give you a lot of insight.

Dear Explorer Guy,
I would humbly suggest that you study some basics of electricity before doling out electrical advice. No offense intended!

 

[Mbrooks420]

Dear Explorer Guy,
I would humbly suggest that you study some basics of electricity before doling out electrical advice. No offense intended!

I agree. You could hook it up to a 10,000 pound battery, as long as it was 12vdc you’d be good to go. Your first step is to track down some electrical diagrams. That’ll tell you where to start.

 

[ajb999]

Thanks, I've been scouring the internet for diagrams. Found a few. I'm finding all the info I can then really going to tear into it this weekend when I don't have to worry about needing it to get to work.

 

[Gary Crist]

Do you have the owner's manual or
what items are on fuse 26? That will help
tell you where to start.

 

[Blk2kXLT]

Something is grounding out. Bad news is that you likely had an issue with the driver door but now if that went backwards burning up the insulation into the dash, you could have a bigger issue. You might want to get a multimeter and hook one end up to ground and start checking to see if any are grounded out.

Only use the recommended amperage fuse from the factory. Upping the amps is not a good idea since the gauge of the wires will not be designed for running 30a where say a 5a fuse was. That's how insulation/wire burns up vs. the fuse.

 

[Deleted member 352605]

Dear Explorer Guy,
I would humbly suggest that you study some basics of electricity before doling out electrical advice. No offense intended!

None taken! I will will be majoring in mechanical engineering next year for my grad work, so maybe they'll talk about that later? that was just what i thought from remembering some stuff for school... granted, it didn't work out perfectly... but that was because some didn't tomis what polarity was... but yes, no offense taken, and i'll see what i learn next year!

 

[8TZX]

Per my 99 Factory Wiring Manual:
Fuse 26 should be a 10 amp fuse. The circuit serves the Battery Saver Relay, Interior Lamp Relay, Interior Lamps, ACC delay Relay and Courtesy Lamps
Fuse 29 should be a 25 amp fuse. The circuit serves the Radio, sub-woofer, CD Changer and Rear Seat Controls.

 

[de]

Oh my. I am glad you're heading to ME school. I'm surprised if you have that inclination that you already don't know a bit about electrical. No offense.

So the first thing is that you didn't have too much voltage. It's all the same in your 12v system. It's not like you'll get a surge in the system. If this is something that simply started happening then wires and connectors/grounds started to corroded, wires started getting hot and worn, wire sheathing somehow got worn out either through heat, friction or chemicals, wires started to touch and voila - short circuits. When a fuse blows, don't simply replace it. There was a reason it blew and now you have to trace it.

Now that you have a what sounds like a melted harness, you have an big problem. The wisest and safest thing to do is replace it all not splice things back together. You will probably have damage in other areas of the harness. You'll need to check all your connectors for corrosion and clean. You can use contact cleaner. You may be able to find a decent harness at a PicknPull yard. Check the connectors and wires to see if they're still pliable. The plastic connectors can easily break since they're old hard and brittle so be careful when prying and pulling and try not to break the locking tab(s). Take your time and be patient like a surgeon. Otherwise, new will be the way to go but expensive. Going to the PicknPull is good education because you can take your time to take apart a vehicle to see how it all works and not worry about damage from being clumsy. It will help you figure out how to take things apart in your vehicle and put back together.

An example of a harness going bad, in the 95-01's, the cruise control harness is an OEM issue where that harness can heat up and cause an engine fire. It turns out the reason for that is oils, road grime and even brake fluid mist starts to coat the harness and get into the connectors. Eventually, that causes the short and fire. There is an aftermarket harness that is supposed to cure that issue. I read somewhere in a Ford bulletin to keep that harness clean and dry to prevent heat build up so it won't short out. I am the **** type where I keep my cars super clean. The engine compartment gets a thorough clean at least once a year, the under carriage, wheel wells, door jambs, etc all get cleaned. Insides get steam cleaned, once in awhile the interior panels get take out for a dusting. Fluids: oil, transmission, differentials and hoses get changed out on a schedule. I have a '96 and a '91 Explorer. The '91 has 320k miles on it now and short of the body rust that developed, you'd think it was maybe only around 10 years old. Well, I take that back a bit now. Here in Seattle, ever since our city went back to salting the roads about 10 years ago during snow, it's added rust to the undercarriage. Grrrrrr!!

Side note on the tranny. All tranny's of all makes and models of cars go bad and thus get labeled as weak and problematic. Why? Because it's the one item that people never think about changing the fluid on a schedule. They put in over a 100k on the fluid then think that maybe they should change it. I won't get into the whole thing here but by that time, it's very touchy. Never flush the tranny - especially if it doesn't get the suggested scheduled fluid change. Just change out what old fluid you can and then let the new fluid mix with the old. It will help to retain some of the particles from the clutch pack to maintain friction for the clutch pack. Even then, after changing and even though the tranny is happy and shifting well, the seals may still blow out because of the nature of what the new fluid is. Manufacturers have gone to simply sealing the tranny these days and say it's a lifetime fluid (whatever lifetime is defined by) because the majority of people never think about the scheduled fluid change like they would with oil. All oils break down and wear out. There are plenty of Youtube videos out now to show how to change fluids in a "sealed" tranny. It's a bit of a pain, but it can be done.

Sorry to hear about your electrical issue. Those things take time to trace down. The key is to always keep the connectors clean, grounds should be clean, check for hardened wires. Over time, resistance builds up, you get heat and that wears out the wiring. I hope this helps you out. Cheers.

 

[Deleted member 352605]

@de ya i completely understand lol... i know enough electrical to replace a light or replace batteries... but... lol

 

[1998Exp]

@de ya i completely understand lol... i know enough electrical to replace a light or replace batteries... but... lol

Well, you already know more than the mechanic who replaced the battery in my wife's ancient car. The only thing electronic in it was the radio, and she complained that it didn't work after the battery was replaced. I popped the hood and found out that he hooked the battery backwards.

 

[de]

@de ya i completely understand lol... i know enough electrical to replace a light or replace batteries... but... lol

Right on. If you truly have that engineering mind, then you'll love going to the PicknPull to teach yourself about how the things are put together and taken apart, especially if you're going into ME. Take the time to examine and think about the systems.

 

[ugjdturner]

Well, you already know more than the mechanic who replaced the battery in my wife's ancient car. The only thing electronic in it was the radio, and she complained that it didn't work after the battery was replaced. I popped the hood and found out that he hooked the battery backwards.

Wow your wife's car has acetylene headlights, the knob at the top of the windshield to manually move the wipers, a crank under the radiator to start it, and no heater motor? Must be a serious antique. That stinks that the so called mechanic hooked the battery up reversed however.

 

[ajb999]

I'm pretty sure it started in the wires running up the pillar to the vanity mirror, rear defrost and wiper, interior lights. The fuse controls lots more including 4x4 system, windows, running lights, glove box light and many others. I didn't put the 30a fuse, previous owner did so probably been blowing before.

I've followed the wire down to where it goes down into the dash, drivers side corner, and can't trace from there. I've pulled all the trim and cluster bit still can't tell. Some wires run to the dimmer switch going by color but they aren't melted or burned there.

I think it might be at my fuse box but using a tab just broke with very little pressure so I don't want to mess them all up pulling it apart.

Originally the smoke seen was coming from the area of the fuse box so I'm wondering if when it grounded out somewhere if it heated up enough to melt some stuff together as my radio fuse keeps blowing too and it's stock and never had any problems with it before.

I'm thinking I might have to pull the dash but don't know how that works with air bags.

Thanks for the help.

 

[1998Exp]

Wow your wife's car has acetylene headlights, the knob at the top of the windshield to manually move the wipers, a crank under the radiator to start it, and no heater motor? Must be a serious antique. That stinks that the so called mechanic hooked the battery up reversed however.

Lights bulbs (the older, incandescent ones) don't care about polarity. Proof: their voltage is reversed 60 times a second on house electricity. Most wiper or blower motors don't care about polarity either, and believe it or not, except for some fancy new ones with anti-theft electronics inside, even starters turn in the same direction, regardless of polarity.

 

[1998Exp]

I'm pretty sure it started in the wires running up the pillar to the vanity mirror, rear defrost and wiper, interior lights. The fuse controls lots more including 4x4 system, windows, running lights, glove box light and many others. I didn't put the 30a fuse, previous owner did so probably been blowing before.

I've followed the wire down to where it goes down into the dash, drivers side corner, and can't trace from there. I've pulled all the trim and cluster bit still can't tell. Some wires run to the dimmer switch going by color but they aren't melted or burned there.

I think it might be at my fuse box but using a tab just broke with very little pressure so I don't want to mess them all up pulling it apart.

Originally the smoke seen was coming from the area of the fuse box so I'm wondering if when it grounded out somewhere if it heated up enough to melt some stuff together as my radio fuse keeps blowing too and it's stock and never had any problems with it before.

I'm thinking I might have to pull the dash but don't know how that works with air bags.

Thanks for the help.

For what it's worth, look for a screw attaching something installed by the previous owner or added to hold a trim panel. It might have penetrated a wire, and because of rather poor contact, ended up drawing just less than 30A, until something moved slightly and the contact improved. I was once provided with a company owned car, and soon found that the dome light didn't work. Someone put a screw to hold a loose piece of plastic trim and shorted a wire to ground, blowing a fuse. Only when I fixed the problem I found out that I had been driving with no brake lights, because they were on the same circuit.
Obviously, it's a very bad idea to "cure" a problem of a blowing fuse by increasing the amperage. Fuses are rated for the gauge of the wiring that they are protecting, and tripling the rating provides a good chance of melting insulation if something happens -- as you found out. As for the radio fuse, I would be looking for something that the previous owner added and hooked to the same circuit. Just my 2c. Good luck!

 

[jmops]

I've got a 99 Explorer that has a short somewhere and trying to put a fuse in #26 blows the second it touches.

My rear defrost, rear wiper, and HUD?(thing above the rearview mirror) have never worked since I bought it. I believe the drivers side door has been replaced as all the wires running from it into the vehicle have non factory connectors and it's missing the rubber cover.
Occasionally the drivers side switch for the drivers window will not go up when pushing up then go down about an inch. I've traced it back to a spliced wire I just haven't had time to fix. I don't think this is part of my problem but just giving info.

So onto the new problem. I went to work, locked my vehicle and walked inside. About 5 minutes later people are yelling for me that my car has smoke coming out of it. Got in and smelled like burnt plastic/electrical but had to work. Go out on my break and windows not working. Start checking things out and no interior lights, running lights, 4x4 lights are flashing on dash. Check my fuses and 26 is blown. Also I think 29, the one for the radio. I work swing shift so don't get off until 11pm so know at the very least I have to get the running lights working. Run get some fuses, try to put one in 26 and arcs as putting in so just put it in to make sure since I've got extra and it blows. Also replaced 29. Driving back to work the radio stayed on but when I went to leave it was blown again. Left work early so I didn't get pulled over for no running lights. Also, the previous owner had replaced the stock 10a with a 30a so problems before.

So today I started pulling stuff off the dash and the front drivers side pillar and the entire way up the bunch of wires that go to the interior lights, vanity mirror, rear defrost and wiper have a burned wire that's melted into other wires at some point. I traced it as far as I could to the dash and it was melted almost everywhere I could see. In a hurry to get to work I cut it with enough slack so I could connect them all later. I know, super stupid but I was in a hurry for work. Still the fuse blows with key out, everything I can see to turn off I did including inside lights.

I tore the dash apart today trying to figure out where the bundle of wires go and after they enter the front drivers side corner of the dash I can't find them.

I'm not sure to go from here because this is my only transportation and I drive 30 mile one way for work. Also I'm not sure why the radio fuse started blowing alongside this. When they saw my car smoking one guy said it looked like it was coming from somewhere on the drivers side.

Sorry for the long post but just trying to give as much info as possible. Any help or suggestions will be greatly appreciated. I'm not the most knowledgeable car guy but have learned a lot working on them but when it comes to electrical systems it's probably my weakest area.

The right way to trace a short that is blowing a fuse is to hook up a VOLTMETER (not an Ammeter or Multimeter in the Amps Mode) ____ACROSS the blown fuse location when you have no fuse installed there. Used in this fashion the voltmeter as really functioning as a milliammeter because a volt meter has a high resistance to current (but is really a milli or micro ammeter in disguise).

When the short exists the voltmeter will show 12V (or your actual battery voltage level) or will show 0V if no short exists. Now you can find the short at your leisure without burning fuses. Inspect all the wiring downstream from that fuse and disconnect any thing hooked to those wires until the short goes away. BTW if the short is really solid (like it blows a fuse) you can just hook up a 12V bulb the same way but the voltmeter will also show up partial shorts and the ones that are really elusive. For example you can hook a voltmeter from the negative battery terminal to ground with the battery cable lifted and it will show you how much leakage your wet or damp battery is doing as long as you have no other parasitic battery drainage like a clock or computer keep-alive loads. It allows you to trace those down to precisely what might be a long term drain on your system. Learned all this from an old timer mechanic when I was in EE school and a part timer in an old-days tuneup shop.

 

[1998Exp]

The right way to trace a short that is blowing a fuse is to hook up a VOLTMETER (not an Ammeter or Multimeter in the Amps Mode) ____ACROSS the blown fuse location when you have no fuse installed there. Used in this fashion the voltmeter as really functioning as a milliammeter because a volt meter has a high resistance to current (but is really a milli or micro ammeter in disguise).

When the short exists the voltmeter will show 12V (or your actual battery voltage level) or will show 0V if no short exists. Now you can find the short at your leisure without burning fuses. Inspect all the wiring downstream from that fuse and disconnect any thing hooked to those wires until the short goes away. BTW if the short is really solid (like it blows a fuse) you can just hook up a 12V bulb the same way but the voltmeter will also show up partial shorts and the ones that are really elusive. For example you can hook a voltmeter from the negative battery terminal to ground with the battery cable lifted and it will show you how much leakage your wet or damp battery is doing as long as you have no other parasitic battery drainage like a clock or computer keep-alive loads. It allows you to trace those down to precisely what might be a long term drain on your system. Learned all this from an old timer mechanic when I was in EE school and a part timer in an old-days tuneup shop.

Hmm, most people don't have voltmeters - or have even seen one. What everyone uses these days (meaning since the 1970s or so) are multimeters. In volts measuring mode they present a 10 Megohm resistance - which means that if you put it across a 12V battery, you'll get a whopping 1.2 microamp current. Your "old timer" method to check for a short to ground will work, assuming that under normal conditions the circuit in question draws much less than 1.2 microamp, which is extremely low - so low that a drop of moisture somewhere across connector contacts will exceed it. Moreover, as you stated, modern vehicles are full of electronics, some of which needs to be constantly powered to avoid losing memory contents (and for other reasons), typically drawing a total of 25-50 milliamps, even with everything turned off. Even an old radio will draw a couple milliamps through its "constant power" wire, whether it's on or off. I am not sure what will happen when you power such circuits through the very high impedance of the meter, because it depends on the nature of the electronics. Some may refuse to draw anything, but some may appear like a short to ground by your method. To summarize, finding a resistance to ground that's small compared to the 10 Meg of the meter is not evidence of anything. The bulb method that you suggested for a dead short will work. You may also modify it by hooking a resistor on the order of 50-100 Ohm resistor across the meter to have it ignore a few milliamps, while responding to something more substantial.
Finally, I didn't get what you mean by "wet or damp battery leakage." No meter hooked from the negative terminal to ground will measure current that's flowing from one terminal to the other across the battery itself -- whether it's internal or on the surface. If you want to measure parasitic drain of the vehicle, disconnect one of the battery terminals and connect it through a current meter. You'll have to wait a while - perhaps several minutes -- for everything in the vehicle to shut itself down before the measurement is valid. If you find excessive draw, repeat the measurement with a fuse removed, to isolate a suspect circuit.

 

[jmops]

Hmm, most people don't have voltmeters - or have even seen one. What everyone uses these days (meaning since the 1970s or so) are multimeters. In volts measuring mode they present a 10 Megohm resistance - which means that if you put it across a 12V battery, you'll get a whopping 1.2 microamp current. Your "old timer" method to check for a short to ground will work, assuming that under normal conditions the circuit in question draws much less than 1.2 microamp, which is extremely low - so low that a drop of moisture somewhere across connector contacts will exceed it. Moreover, as you stated, modern vehicles are full of electronics, some of which needs to be constantly powered to avoid losing memory contents (and for other reasons), typically drawing a total of 25-50 milliamps, even with everything turned off. Even an old radio will draw a couple milliamps through its "constant power" wire, whether it's on or off. I am not sure what will happen when you power such circuits through the very high impedance of the meter, because it depends on the nature of the electronics. Some may refuse to draw anything, but some may appear like a short to ground by your method. To summarize, finding a resistance to ground that's small compared to the 10 Meg of the meter is not evidence of anything. The bulb method that you suggested for a dead short will work. You may also modify it by hooking a resistor on the order of 50-100 Ohm resistor across the meter to have it ignore a few milliamps, while responding to something more substantial.
Finally, I didn't get what you mean by "wet or damp battery leakage." No meter hooked from the negative terminal to ground will measure current that's flowing from one terminal to the other across the battery itself -- whether it's internal or on the surface. If you want to measure parasitic drain of the vehicle, disconnect one of the battery terminals and connect it through a current meter. You'll have to wait a while - perhaps several minutes -- for everything in the vehicle to shut itself down before the measurement is valid. If you find excessive draw, repeat the measurement with a fuse removed, to isolate a suspect circuit.

 

[jmops]

Oh my, You miss the point...which is to isolate all the loads connected to the fuse without burning up a couple of boxes of fuses playing guessing games .....or burning up shop hours chasing a hidden fault, resulting in the shop eating some billable hours to save face. A quick, correct solution without just throwing parts at the problem pays off in terms of future business.

If you disconnect everything in the network of wires supplied by that fuse, at the point where each load receives its power and there is still a short (limited to 1.2 microamps by the meter) then you have a wiring harness problem. If the circuit is now "open" then look for the problem in one of the loads you disconnected by verifying each one by current measurement, smoke, melted wires, whatever, or trying to blow yet another fuse, your choice. I didn't specify the meter had to be an old d'arsonval one or an electronic one that imitates a d'arsonval one in terms of input impedance, etc. A "modern" multimeter, d'arsonval display or not, is just a switch box with circuits that apply the input voltage, ampere, or resistance signal into a common d'arsonval or digital display.

As far as the connection to the ground side of a battery, if you draw the circuit, remembering that the plus side of the battery is still connected to its plus cable, then any surface dirt, acid traces, etc on the surface of an old battery will provide a current path that will drive the meter. You can simulate the effect by tying a high resistance in parallel from the plus terminal to the negative one around the battery. That's just a side topic I threw in there.