Like the title says, my headlight fuse blows after a few minutes. Its done this twice, and I'm wondering if anybody has any ideas of where I can look for a problem. I know to look for any wires that may have rubbed through their insulation and are grounding out. The fact that it takes a little while to blow, is a little strange to me.
Headlight fuse blows after 10 minutes (1 Viewer)
- Thread starter mathblaster
- Start date
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emtee
HAHA...Wait, Wut?
Mathblaster,
A few minutes after....?
Were you swapping out a headlight, doing wiring work or...? Run a ground continuity test on an open circuit to sniff out ground faults. Using the right caliber fuse?
Good luck; electrical gremlins are the debbil...
A few minutes after....?
Were you swapping out a headlight, doing wiring work or...? Run a ground continuity test on an open circuit to sniff out ground faults. Using the right caliber fuse? Good luck; electrical gremlins are the debbil...
emtee
HAHA...Wait, Wut?
Ah, c'mon...where's your sense of adventure?
I have used nails before(when I was like 16-17).......if I didnt have a nail.....I would have used the 22
Mythbusters did a show on the 22 in the fuseblock, they got it to fire actaully
Mythbusters did a show on the 22 in the fuseblock, they got it to fire actaully
Ah, c'mon...where's your sense of adventure?
emtee
HAHA...Wait, Wut?
I've never been gutsy enough to put ordnance in there, but I did use a piece of gum wrapper held in place with the blown fuse once. Didn't know what the problem was in the lighting circuit and my hope was the foil would go before I torched the whole wiring harness... Got me out of the woods!
sounds like the connection on either side of the fuse is bad (oxidized). the fuse may be blowing after it heats up from high resistance. you should be able to feel it getting hot before it blows. if this is the case, clean up the contacts with some sand paper or scotch brite and put some dielectric grease on there upon reassembly. in fact this same problem could occur in the switch or any other wire on the circuit and create resistance as it warms up. check the fuse holder contacts first though.
I have had one or the other contact loosen and short out like that in the past. The rivet was broken and I just replaced the fusebox: never happened again.
Are you driving when the fuse blows? Or just sitting there idling? You may have an intermittent short somewhere in your headlamp circuit (thats why the fuse is there...headlamps are more expensive to replace than fuses). I had this happen to me with one of my old rigs. PITA to locate.
When tracking down my electric mess, I unplugged the wires at the firewall from the back of the fuse block one by one and figured out which "bundle" of wires were the cause... For example, it helped me narrow down my search to the rear. What all doesn't work when the fuse blows?
"...sounds like the connection on either side of the fuse is bad (oxidized). the fuse may be blowing after it heats up from high resistance"
x2 - or someone has replaced the wire going to the headlights with too small of a gauge wire, it is heating up, high resistance... and .....blown fuse
Especially if one has put high O/P headlights in there (ie 100+W)
x2 - or someone has replaced the wire going to the headlights with too small of a gauge wire, it is heating up, high resistance... and .....blown fuse
Especially if one has put high O/P headlights in there (ie 100+W)
- Thread starter
- #12
I haven't done any electrical work on the cruiser for a while, so I can say I didn't swap anything in that is causing it. It does have a new fuse box and standard headlights. The fuse blew when I was idling in the driveway. I replaced it and it blew right away. There is a lot of snow up here. Would it be possible that my highbeam switch, that is in the floor, could be getting moisture in its self causing the short? Or is the headlight switch known to be trouble? My other guess is just that something is loose and bounces around then shorts out.
Mine would blow when I had the insulation off of the wiring connector to the front driving lights. I'd hit a bump and the connector would short against the fender. New insulation cured the problem.
I've had experience with that before. Could be anywhere on the headlight wiring harness. Check under the hood first. Pick up the harness and check for any wires rubbed through.
check the wires that run through the rear door to the number plate lights, if there is no rubber grommet fitted it will rub through and blow fuse's........
fjwagon
SILVER Star
I think you mean current goes up and resistance goes down which gives an indacation of a short causing the fuse to blow. If you increase resistance and keep the voltage the same you would have dim lights. Maybe I'm wrong
sounds like the connection on either side of the fuse is bad (oxidized). the fuse may be blowing after it heats up from high resistance. you should be able to feel it getting hot before it blows. if this is the case, clean up the contacts with some sand paper or scotch brite and put some dielectric grease on there upon reassembly. in fact this same problem could occur in the switch or any other wire on the circuit and create resistance as it warms up. check the fuse holder contacts first though.
I think you mean current goes up and resistance goes down which gives an indacation of a short causing the fuse to blow. If you increase resistance and keep the voltage the same you would have dim lights. Maybe I'm wrong
You are right. If there was a bad or oxidized connection, small wire or heating, the resistance would go up and less current would flow. This would make the lights dim, not blow the fuse.
The oxidation acts as a series resistor which will cause heating at the bad connection. In turn, you suffer a voltage drop across the bad connection. The headlights want a certain amount of power, which is the product of voltage and current, so the current increases in the headlights to attempt to satisfy Ohms law....pop goes the fuse.
It doesn't work that way. Ohm's law: I = V/R
The maximum input voltage is regulated and it doesn't increase. The bad connection acts as a resistor, so not only does the voltage drop, but the current drops too. The lights will dim with a bad connection, but it will not blow the fuse.
