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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Cosmetic and Lighting Modifications (exterior/interior) > Fuse upgrade dangerous?



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      05-02-2009, 10:44 AM   #1
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Fuse upgrade dangerous?

Hi guys,

I have replaced my lowbeam fuse with 10 amps extra. OEM fuse was 40amp and I put a 50amp. The reason is I added HID's and the lights used to flicker when truns would be turned on, and it seems that with new fuse the flickering is rerduced. Do you guys think it is dangerous? Should I go back to the 40 amp fuse?

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      05-02-2009, 10:46 AM   #2
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You should never put in a larger fuse than what it came with from the factory. The size of the fuse will not effect flickering. The fuse is either open or closed. If the HIDs drew too much amperage, the fuse would just blow.
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      05-02-2009, 11:24 AM   #3
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I would agree that the fuse would blow. Why don't you switch back and see what happens? If it goes back, then maybe the person who posted about adding a 4700 uF capacitor was right, and that little extra metal made a difference, (acted like a capacitor.)

(I need to verify if it was 4700 uF or some other value...)
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      05-02-2009, 11:27 AM   #4
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Yup, it was 4700 uF. If the problem goes back, the capacitor is the way to go, not a fuse.
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      05-02-2009, 05:41 PM   #5
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The fuse is rated to protect the size of the wire. It will blow before the melting point of the wires. You should never put a bigger fuse in than what the factory provided.
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      05-03-2009, 02:24 AM   #6
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flickering on the low beams if a different issue than it is with the fogs as i have discussed in another thread. The flickering you see is most likely due to a very inefficient ballast you have powering your HIDS. This occurs cus when you turn them on the system isnt designed to supply that much power all at once (HID initial current draw can go up to 11amps) 14volts*11 amps for each ballast is about 154 watts of power (stock only draws 55watts) of course your 40 amp fuse also powers other items like your city lights and what have you...i have seen several times where it is needed to increases the amps on a fuse to get it to work. Good thing is that our wiring is pretty good and the safety factors are pretty high so i would say that a 50 amp fuse is not going to be a problem. Of course its your car and what happes is on you but if it was my car i would be perfectly confortable with 10 extra amps. hope that helps


-Jon
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      05-03-2009, 02:26 AM   #7
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Quote:
Originally Posted by Sunstealer View Post
The fuse is rated to protect the size of the wire. It will blow before the melting point of the wires. You should never put a bigger fuse in than what the factory provided.
of course this is very true but there is also a line that you can push...me personally i believe the wiring can support than extra 10 amps with out being an issue. but its a risk you take..
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      05-03-2009, 10:59 AM   #8
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If it took that 154 watts at 12V initially then I think the fuse would blow. That's essentially triple what it was putting out originally! The ballast probably includes a step up transformer to produce the 10k volts or something to that nature, the other side of the Power equation. (You can manipulate the power using either V or I, or both.) Hence the warnings not to change the bulbs yourself, you could essentially kill yourself! It shouldn't take that much amperage at any time. Flickering is inconsistent power, so a capacitor is still what I believe to be the best solution.

The tolerance is there for a reason. Is there a higher risk of fire in very hot weather, yes there is...

Quote:
Originally Posted by JonLerd View Post
flickering on the low beams if a different issue than it is with the fogs as i have discussed in another thread. The flickering you see is most likely due to a very inefficient ballast you have powering your HIDS. This occurs cus when you turn them on the system isnt designed to supply that much power all at once (HID initial current draw can go up to 11amps) 14volts*11 amps for each ballast is about 154 watts of power (stock only draws 55watts) of course your 40 amp fuse also powers other items like your city lights and what have you...i have seen several times where it is needed to increases the amps on a fuse to get it to work. Good thing is that our wiring is pretty good and the safety factors are pretty high so i would say that a 50 amp fuse is not going to be a problem. Of course its your car and what happes is on you but if it was my car i would be perfectly confortable with 10 extra amps. hope that helps


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      05-03-2009, 06:19 PM   #9
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I put back the 40amp just to be safe, because my lighting has been acting weird, and hopefully I can resolve other problems...
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      05-03-2009, 07:11 PM   #10
jzchen
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Definitely give the capacitors a try, someone else is trying them to great effect on flickering! We are trying to resolve the error now...
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      05-04-2009, 02:46 AM   #11
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Quote:
Originally Posted by jzchen View Post
If it took that 154 watts at 12V initially then I think the fuse would blow. That's essentially triple what it was putting out originally! The ballast probably includes a step up transformer to produce the 10k volts or something to that nature, the other side of the Power equation. (You can manipulate the power using either V or I, or both.) Hence the warnings not to change the bulbs yourself, you could essentially kill yourself! It shouldn't take that much amperage at any time. Flickering is inconsistent power, so a capacitor is still what I believe to be the best solution.

The tolerance is there for a reason. Is there a higher risk of fire in very hot weather, yes there is...
thats incorrect...14 volts at 154 watts is just under 11amps per ballast. (P=VI) at 2 ballast he is initially drawing a peak draw of 22amps out of the 40 or 50 amp fuse that he has in. This all happens for just a few seconds and then drops to a mere 3.2 amps. The ballast does have a digital inductance circuit that steps up the voltage to just under 23kV at start up and then drops to 85volts at steady state. The danger signs that you could kill yourself are very true especially if you have a pace maker but i have been shocked by HIDs befoe and if your perfectly healthy it will only give you a good buzz and then some minor burn marks but that is all...the way the ballast converts power is by upping the voltage at the price or current...and it is the current that will kill you not the voltage. (reason why stun guns and tazzers are non-lethal weapons same principal)

just stating facts
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      05-04-2009, 03:01 AM   #12
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Thanks for correcting me. I didn't do the math... Does the fuse only run the low beams? I haven't checked that either.
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      05-04-2009, 03:14 AM   #13
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Quote:
Originally Posted by jzchen View Post
Thanks for correcting me. I didn't do the math... Does the fuse only run the low beams? I haven't checked that either.
on our cars since its bi xenon the electronic shutter driven by a solenoid is all that is powered to get highbeams...which is also driven by the fuse that powers the whole head light....my guess is each head light fully functioning draws this much power


hids 35watts
turn signals 24watts
angel eyes 35 watts max(although its usually under driven my guess 15 watts?)
high beam (bixenon shutter) 5 watts tops.

my guess top 100 watts max steady state...factor in an additional 10 amps when the hids first start up so your at about 20amp each headlight....


also if the weather was hotter the effects on a fire hazzard is still not worth factoring in...at the temps it would take for a wire to over heat and burn its insulation we are talking a few hundred degrees on the hottest day your looking at a +- 30-40degree swing which is only a fraction of what the insulation is rated at. I really thing an 50 amp fuse on a 40 amp circuit is safe.
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      05-04-2009, 12:52 PM   #14
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Thank you guys on your inputs, it is very helpfull
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