I stand corrected, I took a sec to draw out the circuit. The current would not increase, instead decrease due to the series impedance. However, the voltage drop across the bad connection will cause a lower voltage at the headlights, hence dimming. The more corrossion, the higer the impedance, the higher the voltage drop, the dimmer the lights get.
Headlight fuse blows after 10 minutes
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fjwagon
SILVER Star
You can not have an increment in resistance and current at the same time and have voltage remain the same when you have a bad connection. Current will increase which creates heat if you don't have the correct gauge wire. The resistance will go down and mimic a short and if you leave it long enough to the point it will blow the fuse because it can not handle the load. If the wire is long enough or gauge is big enough that in itself could act as a resistor. But that is not the case here.
I had a similar problem and it ended up being the wire headed to the little light on one of the rear fenders. It was just by luck that I found it. Happened to be looking at it in the dark and saw the spark. Since then it's worked fine. I had gone through a handfull of fuses before I found that though.
fjwagon
SILVER Star
Huh, about the only time word "impedence" is brought up at work is if we're working with caps or inductors. And were talking about a DC circuit not an AC circuit. Just remember this when you're troubleshooting your 40: If voltage goes up, current will go up as well but resistance will stay constant and if we have bad connection, resistance goes up and voltage stays constant, current will go up.
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I should have been clearer, I meant a steady state DC circuit. Here is something that may clear this up a little (stolen shamelessly from the web):
"Resistance is quite simple to understand. Everything in the universe has electrical resistance. It so happens, that even wood, rubber, plastic, and glass do in fact conduct electricity just like copper wires do. Their resistance, however, is so very high, that we use them to "insulate" wires, or keep them protected from other things (namely, other wires). They are called "insulators", for obvious reasons.
There are materials, whose resistance is not high enough to be insulators, but is too high to be a conductor. These have a practical application as "resistors", or components whose purpose it is to resist. The amount of resistance these devices have (or the resistance of anything, for that matter) is measured in a unit called "Ohm" (pronounce "O - m"), and is represented by a symbol called the Omega. Although a resistors value (in Ohms) changes slightly with temperature and with age, for practical purposes, it is the same always, no matter what the electricity is doing.
Impedance, however, is dependant on a property called reactance, and frequency. Impedance only exists where there is AC, or fluctuating DC (AC with a DC bias). "
We do forensics where electrical is a suspected cause of a fire, so the "industry" is a little different that if you are in design. I did that for a while, so I understand why you think I am crazy for calling it "impedance" instead of resistance. Just a creature of habit here.
"Resistance is quite simple to understand. Everything in the universe has electrical resistance. It so happens, that even wood, rubber, plastic, and glass do in fact conduct electricity just like copper wires do. Their resistance, however, is so very high, that we use them to "insulate" wires, or keep them protected from other things (namely, other wires). They are called "insulators", for obvious reasons.
There are materials, whose resistance is not high enough to be insulators, but is too high to be a conductor. These have a practical application as "resistors", or components whose purpose it is to resist. The amount of resistance these devices have (or the resistance of anything, for that matter) is measured in a unit called "Ohm" (pronounce "O - m"), and is represented by a symbol called the Omega. Although a resistors value (in Ohms) changes slightly with temperature and with age, for practical purposes, it is the same always, no matter what the electricity is doing.
Impedance, however, is dependant on a property called reactance, and frequency. Impedance only exists where there is AC, or fluctuating DC (AC with a DC bias). "
We do forensics where electrical is a suspected cause of a fire, so the "industry" is a little different that if you are in design. I did that for a while, so I understand why you think I am crazy for calling it "impedance" instead of resistance. Just a creature of habit here.
That's a good way to put it. I just realized we aren't helping on this thread because any corrossion would not cause a blown fuse. So, I am not sure where the problem lies. I can't really figure out what would cause it to blow after 10 minutes, unless maybe a bad voltage regulator that allows ramp up after the alt fully charges the battery????? Still, the voltage shouldn't exceed around 14V, correct? That shouldn't be enough to pop the fuse.
No.
V = I/R
Both voltage and current go down as resistance goes up. Resistors lower power (I*R).
I agree PinHead. What I am trying to figure out is why, after some time, the fuse would blow. If there is a short somewhere, it should pop immediately. All I could think of is the bad voltage regulator, but I think that theory doesn't really hold water.
fjwagon
SILVER Star
I scewed it up agian.
I had it the first time. Voltage stays constant(12 v battery source), resistance goes down, and current will go up.....causing the fuse to blow. This is what I was trying to say.
I had it the first time. Voltage stays constant(12 v battery source), resistance goes down, and current will go up.....causing the fuse to blow. This is what I was trying to say.
fjwagon
SILVER Star
I had a problem where the marker light would blow a fuse randomly. I checked for a loose connections and could not find anything that would cause it to go bad. Finally figured out I had wire that was dangling and hitting the right bump or turning just right would cause it blow.
Usaully when you have a delay in blowing a fuse and it's random I usually look for a bad connection like making sure you have clean connections at the head lights and the fuse holder is clean. Also check your grounds. Just because it connected it does not mean it's actually completing the circuit. They will oxidize and cleaning them is the only way to make sure it's making good contact. Using contact cleaner will make your job easier.
Usaully when you have a delay in blowing a fuse and it's random I usually look for a bad connection like making sure you have clean connections at the head lights and the fuse holder is clean. Also check your grounds. Just because it connected it does not mean it's actually completing the circuit. They will oxidize and cleaning them is the only way to make sure it's making good contact. Using contact cleaner will make your job easier.
