main power wire for interior,exterior,turn lamps,ignition shorts out

[broncobuckinaround]

started out i was driving to work, suddenly the car shuts off and smokes come out of the hood. the black with orange stripe wire fusible link had fried and caught fire.

so i began to unravel the loom and traced to the fuse panel and the headlight switch.

i figured it shorted because it got a ground, well using s test light confirmed it. the blk/org wire was being grounded. so in tracing it i found it fuses into multiple things. one being the dome lights. its fused into them so by pulling the fuse the ground went away. simple yeah ok dont need dome lights got flashlights everywhere.

any how i fixed the burnt wires by cutting away all the burnt parts and splicing in a fusible link (30amp fuse).

the problem still exists but only when i turn on the headlights, i found a pin out on here that says what the wires are and where they go. heres the link so anyone reading this can follow me, http://www.broncoiicorral.com/library/headlight_switch_wiring.shtml

H,B2,and I all have a constant ground. doesnt matter if i pull the switch, or the car is running or if the ignition is on or off.

b2 ends up being power for the turn lamps, if i take the bulbs out the ground goes away. thats as far as i made it with that. but thats confusing.

i need further help taking this on. im a great mechanical person. just very bad with electrical.

 

[ab_slack]

A test can fool you at times. Things like the headlights have such low resistance that they can effectively look shorted. An ohm meter can help distinguish between low ohm and a short.

To blow a 30A fusible link on a 12V system you need a half an ohm or less.

Comment about the dome lamp, if that had another fuse in series, what was the size of that fuse? That fuse should have gone long before the fusible link.

You say the problem exists with only the headlight on. Is that using the test lamp or is it blowing fuses? If using test lamp, unplug the headlights at the headlight while doing diagnosis. Your test lamp is probably being fooled. Does it go away with the headlights unplugged? If so you were probably chasing a ghost. Very rare, practically impossible fot headlight to fail shorted, but you can always measure the headlight directly with an ohmmeter.

If the short doesn't go away when you unplug the headlights, you can continue to explore with the headlights unplugged and avoid some potential confusion. Did the original failure occur while the headlights were on? If not then the problem probably is not in the headlight circuit.

A general comment, fusible links are generally used between power source and distribution/fuse panel to cover the event of a short occurring before the panel as the branch circuit fuses will protect from there. The fusible link also protects against the problem of people putting bigger fuses to solve fuse blowing problems. My point is that tends to lead to one of two possibilities. First is that the short occurred at or after the fusible link and before the distribution/fuse panels. Or there is some sort of modification after the fusible link. By modification I include one or more circuits with wrong fuse values. Or extra circuits added in at the fuse panel. or otherwise spliced in after the fusible link.

If the fault isn't before the fuse panel, the normal fuses should blow before a fusible link lets go. What happens though someone may experience an intermittent short in a branch circuit blowing a fuse. Replacing the fuse always gets it working and days, weeks later. Eventually someone sticks in a big fuse and the problem seems to go away. The problem hasn't gone away, all that means is the intermittent isn't enough to blow the larger fuse. It could then be burdening the fusible link, but because the fusible link takes much more energy and time to burn up, it seems fine. Eventually either the intermittent stresses the fusible link till the point it burns up while the fault is still only intermittent, or the fault goes from intermittent to a complete short taking out the fusible link. A bad situation as the branch circuit being a smaller wire often can end up getting very hot and short to other wires in the process or catch fire.

So if you swapped out a fuse cause of intermittent fuses blowing, and that circuit gets power thru the fusible link in question, check that branch circuit out. If you didn't do anything like that, if there were any prior owners see if one may have put in a big fuse where it shouldn't' go.

If all fuses look okay, then pull the fuses and focus on the area between the fusible link and the distribution/fuse panel.

As a test, disconnect the fusible link at the power source and insert a 5A or 10A fuse and see if you can apply power to the circuit without blowing the fuse. With all branch circuits off it shouldn't draw much power. If it blows a fuse you know none of the branch circuits are responsible. If it doesn't blow a fuse, well wiggle the harness see if you can get it to blow. That can help uncover an intermittent.

If that doesn't do it, connect one branch circuit at a time and see if the branch circuit fuse or that temporary fuse blows. This can be a big trickier as the temporary fuse may be rated too low for the particular branch circuit. As you test out one, wiggle the harnesses involving each branch circuit. As you have checked one pull that fuse out before putting the fuse for the next.

I hope at this point I didn't confuse you thoroughly.

Getting back to the headlights, if you are pretty sure it is in the headlight circuit, check the high/low beam switch in the steering column. The full headlight current goes thru that switch and it tends to be a weak point. That switch tends to wear out before others cause of how often it gets used and as contact gets poorer it starts to warm up. I have had a couple of those switches melt. In doing so the mating connector melts and contact in the cable harness starts to go bad so when replacing the switch, it continues to get warm. The big symptom is that high beams start to flicker or headlights go out entirely, but with things melting there can be significant chance of something shorting there.






from that panel that have larger fuses in there than they are supposed to be such that

 

[broncobuckinaround]

thx so much. and yes confusion is massive. not knowing about electrical makes harder. my brother is a uti grad. he says he knows some. so with your info im sure he can make sense of it and get us further in solving this.

ill post back when i have more info and answers to your questions.

 

[broncobuckinaround]

for the dome lights it was a 15amp fuse and no it didnt blow. but was grounded before the fuse on the dome light side. i didnt put in a bigger fuse i just pulled out the bulbs. and the wire wasnt grounded anymore.

when i pull out the switch to turn on the headlights yes using a test light, also i can take the fuse and see it arcing when i just barely put it in. and not to long after it will blow the fuse.

no the light stays on. it goes off when i unplug the switch it did once and did with out once. the one time it did do it with the light off was because it ground due to the dome light circuit was grounded solid. and was a constant. so by talking out those bulbs the constant ground went away. and i was able to hook up the new fuse next to the starter solenoid. and then that was still blowing. lol thats why were here.

im not sure its a problem but.......i installed off road lights. my power source is the highbeam wire for the headlight and my grounds is frame. so they dont come on unless i turn off the high beams. thought it was cool. but not sure if it contributing to the problem.

your asking if its before or after the panel. well this blk/org wire splits in two after it passes into the cab. one goes to the fuse panel and the other goes into the headlight switch. knowing if i unplug the switch the ground to the blk/org wire goes away.

lead me to finding ground on the three wires i noted in the first post.

i traced B2 and it goes to the front turn lamps. the light on the fenders as well. now by taking out those bulbs the ground on the wire goes away.

i also traced I to the fuse panel which is a 5amp fuse. and i couldnt see anything past that. by the description of the link provided this wire powers the instrument cluster. that was unplugged but ground was till there. even if i pull the fuse.

H goes to the turn signal switch on the column. ive replaced that once allready because it fell apart. so its new. and of course if i unplug it to, it to will have the ground go away.

ok i did the test with the 5amp fuse cuz thats all can spare. i unplugged the head lights in doing this test.

i hooked the power wire and inserted the 5amp fuse. shook, pulled, twisted, hit,slapped the whole loom. all the way to each connector checking the fuse after i got to each connector. and nothing happened. so i pulled the highbeam lever cause of curiosity to see if the offroad lights would come on and it blew the fuse. omfg go figure.

on your last comment. you said the head lights will flicker. just before i parked it because it worried me they were flickering. but not just the head lights it was dash and the head lights. plus my battery light was on and flickering too.


ok now that all you questions are hopefully answered. lol. i like the fact you want so many details. if i could rate you i would rate you the highest

 

[ab_slack]

A big secret about light bulbs. When the filaments are cold they tend to be much lower resistance than when hot. So even small bulbs can look like a short. That is probably what the dome light did to you. The short going away when you removed the bulb is strongly suggesting nothing wrong, at most the bulb is shorted (unlikely).

The 5A fuse blowing when you turned your high beams on was probably due to those extra lights still being connected. To repeat the test you probably need to disconnect those lights too. If those aux lights were not connected, then the fuse blowing when you switched to high beams would indicate a short in the high beam circuit but from what you said I think you realized it was the headlights.

I have the full set of wiring diagrams and took a look but following them isn't exactly easy. I can't see where the fusible link comes into play.

So just speculating here.

Are you able to find a headlight fuse? I've heard of fusible links used with headlights so less subject to intermittent failure as a headlight fuse blowing can leave someone in the dark literally.

So here is my theory.

You tapping the high beam line added additional load to the high beam circuit that it can't handle. Even if the wires can handle it, I can tell you the high/low beam switch can't. It has enough trouble with the normal load.

Did this problem start while your high beams were on by any chance?

It is entirely possible that the extra load burned out the circuit.

Consider this, any lights that significantly improve lighting while high beams on probably draw nearly as much power or more. It is okay to hook up little aux lights, but not something like that on the existing circuit.

How I would have done it is get a auto relay rated for the kind of current the lamps need. there are 20A and larger ones. I would connect one side of the coil to return of the frame, the other side of the coil to the high beams. This way the relay energizes when the high beams are on. Then I would run a extra wire from the battery with a fuse in line to the relay contact. The other side of the relay contact wire it to lights. The lights then have their own return wire to the battery negative. Thus the lights come on only when high beam power gets to the relay coil.

 

[broncobuckinaround]

fantastic on that last part i would have never thought about that.

however i got ahold of friend who work in an exotic racing shop in las vegas called exotic racing.

hes my guru but insanely hard to get in to contact with. so he guided me around explaining the exact thing you have been. so learning from you already made it easier to follow him. thax for that btw.

so he had me unhook the positive side of the battery and put my test lead on the pos post and touch the termial. it lite up. i asked him what that means and he said its drawing power somewhere. i asked how do i find that out. he said start unplugging things til it turns off. laughing hard, i started. i finally got to the headlight switch and the light turn off. he said that its directing current where it shouldnt go and advised me replace it.

what are you thoughts. i want your input too. please and thank you. oh and i unhooked my off road lights too.

 

[broncobuckinaround]

it didnt fix it. but on the plus side my lights are brighter.
somtimes the alternator quits charging. and when i pull the harness apart it blows the fuse. while its running and the alt is charging that fuse gets hot regaurdless if the light are on or off.

i dont know whats going on now

 

[ab_slack]

The test he had you do I presume was with the ignition off. Ignition on probably wouldn't have told you much as there would be a number of things drawing load.

With the key off, the test was essentially to see if there was some parasitic load. In other words a load that isn't supposed to be there and in simplest form can drain your battery when the ignition is off.

The typical symptom of a parasitic load is the car seems perfectly fine on a day to day basis but if you don't drive the vehicle for some period the battery is always dead. The load is small enough that it doesn't drain the battery in a the course of the typical interval between times you drive so you are recharging the battery and never see the problem. (BTW a damaged battery that self discharges can show the same symptom)

Many if not most cars have some sort of parasitic load when off but it is designed so that compared to the battery capacity it won't drain the battery much even if vehicle sits for extended period. Think alarm system, clock, electrical door locks, etc.

What I think he was doing was having you look to see if there was an abnormally high drain and isolate it.

Depending on your test light though, the load could be very small so might not relate to your problem.

I guess it isn't clear to me what your problem is at the moment given all you have gone thru.

You replaced the fusible link. And quite correctly I think you recognize the problem wasn't the fusible link itself, that was just the symptom.

So where are you at now?

Have you re-applied power and tried things out or are refraining from that because you haven't found the real problem yet?

Or have you re-applied power and found some problems. If so what are the current symptoms?

If you are stuck at not putting power back on because you are looking for the root cause. I would be tending to lean towards those extra lights you hooked to your high beam as the cause. Disconnect those for the time being. Once you are satisfied everything is working again then hook them up using the relay as I suggested.

There is always concern with a fusible link about what else may have been damaged. I would be concerned about the lights on/off switch and the high/low beam switch as they saw the overload. I think what you just said was you replaced the lights on/off switch and the lights are brighter now which is probably because the contacts weren't good which could very well have been due to damage by the overload but also just age at this point.

Last thing would be damage to any wires immediately around the fusible link as that got hot when it opened up. Such damage to other wires should be fairly obvious. If the fusible link was done correctly it shouldn't have damaged any other wires tho.

 

[ab_slack]

I see RonD answered you on TRS. Ron always has good info.

http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Headlights_1983to1989.JPG

This diagram gives a quick summary of the circuit and is infinitely better than the detail full diagrams I have. I actually have another book that shows this exact diagram, I forgot it had specific circuit diagrams. Oh well.

Anyway it confirms about what I was expecting. That there was no fuse in the headlight circuit. It is possible the extra lights just overloaded the fusible link and your lights and everything that come off the fuse panel that is also fed goes out.

From that fusible link, any problem has to be in the lamp circuit or wiring as shown or in the wire to the fuse panel. It is very doubtful that there is any problem downstream of the fuse panel as that individual fuse would have blown first.

 

[broncobuckinaround]

my friend i were talking about it again and again over the last few nights. he had me check the amps my alternator was putting out. which is 65amps. he said the surging from it could overload my little 30amp fuse i put in and that could relate to why its popping.


i unhook the lights, he said the same thing you did. so they are off the circuit and i fabbed a 50amp big maxi in the line. nothing gets hot now just the charge wire coming from the alternator. everything stays cool for the most part. and the alt is putting out 14.56v. guessing because the i ran it a lot with the alt charging. i didnt know it wasnt charging all the time. found that out later on.

in my thoughts and hopeing in yours too. the reason behind the short was very large overload to the circuit cause by the big offroad lights. and possibly to the fact that the fusible link was older and couldnt hold the current anymore.

ive put power back to everything and drove it around. seems fine for now. i didnt go far cuz this bronco has got me walking more back more times than any car should.

i would like to up grade the rest of the links for good measure if thats a good idea. would you suggest i do that. i dont want any other link being weak and frying because of this whole thing. and was it smart to put the bigger fuse in

 

[ab_slack]

Sounds like good results.

I doubt the age of the fusible link was a big factor. The lights, yes that is it and I concur.

To get your lights working, just go with that relay suggestion with separate wires to the battery with positive leg fused near the battery.

 

[broncobuckinaround]

well so far so good. i havnt had anymore problems. i took it out rabbit hunting and it ran good for 5 hrs straight. still putting out 14.56v out of the alternator.

 

[ab_slack]

Good, nothing else got smoked then.

 

[efilnicufecin]

look!!