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Discussion Starter #1
What voltage value is applied to which filament?

I'm popping DRL 10amp fuses lately and wondering if I should up the fuse ampereage to 15 amp or change my bulbs. I will measure current flow tomorrow during daytime because you can't check it at night unless you apply light on sensor on top of dash. Fuse holds for a couple of days then next thing you know no DRL. I might figure it out by myself but always nice to have a second opinion.
 

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Discussion Starter #4
No HID's... And don't have to pull the fuse it's already open.....lol

Well I changed bulbs for JP Thunder and think they might draw a little more current than OEM. They sure spit out a lot of light. Just wondering if wires and circuit can handle a bit more current. If not I'll get some silverstars or something.
 

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Discussion Starter #6
Just did some quick calculation and these would draw almost 4 more amps per pair on low beam at full 14.3 volts, but I don't know what running voltage is. I know it is lower than 12 because when night lights come on they get brighter.
 

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Discussion Starter #8
Low beam is 80Watts instead of 55Watts if DRL uses low beam. I will check tomorrow what each individual filament is fused at.
 

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Coby, the stock bulbs and also the Silverstar Ultra's that I run are 55/65 watt. It sounds like the bulbs you have draw too much.
 

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Discussion Starter #10 (Edited)
OKay sorted everything out today.
1 DRL uses low beam filament.
2 At reduced battery voltage. So 9-10Volts @7.56amps with engine off.
3 Closer to 10Volts @8.36 amps with engine running. If you do the math and it doesn't add up it is because filament resistance increases with heat so the more current flows through the hotter it gets and the more resistive the filament gets.
4 Well 8.36 amps running through a 10 amp fuse is cutting it close, engineering practice is to never exceed 80% of rated value (I'm at 83.6%).
5 Both low and high beams are fused at 10 amp for each filament. So I'm expecting to blow high beam fuses soon. Low beam are in specified ampereage limits.
6 Now I checked wiring size and this guage is good to 25 amps at +40°C or (104°F)
7 So if I blow these again I will up the fuse to 15 amps from 10.
8 Only piece of electronic that might not hold-up is the relays and I'll replace them when they go.
These bulbs don't draw too much they just draw more.
 

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Bulbs

If you wish not to diagnose problem for fuse blowing... Replace aftermarket bulbs with OEM to see if problem goes away. (As you know, simple procedure)I think you will find aftermarket bulbs will be your problem.

I have seen the G5/Cobalt totally lose the DRL function altogether, but did not blow any fuses or have any DRL circuit irregularities. The issue there was an internal aftermarket bulb issue.

Again, switch back to OEM to see if problem occurs. NEVER upgrade a fuse to compensate for other problems. That can easily be a VERY expensive mistake!!!:cry:

423
 

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Discussion Starter #13 (Edited)
I know I am running at the limit of this circuit, but there aren't any 11 amp fuses. I also know that tolerences are 20% +/- depending on manufacturer. So tonight I tested three different manufacturers 10amp fuses. The ones purchased at GM dealer (AC Delco) all failed around 8.5 amps. These are the same that were in the car. Princess Auto were closer to 10 at average 9.7 amp. This is the one I installed in the car for now.
But I have a back-up. The ones purchased at Auto Pro failed at around 11 amps so if the Princess Auto fail I will try the Auto Pro ones. If these fail I'll go back to OEM bulbs.
 

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Discussion Starter #14 (Edited)
OK, update the princess auto 10 amp fuse is holding up so far.....I have the same bulbs (9007 JP Thunder) in my Mitsubishi also fused at 10 amps and I never had a problem.
 

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Discussion Starter #15
Still holding up!!!
 

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Discussion Starter #16
Like the energizer bunny, still going!!!
 

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Discussion Starter #17
2 weeks later DRL and fuse still OKAY, so I'm classing this as problem solved.
 

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If filament resistance increases with temperature then when it heats up there will be LESS current, not more. I=E/R, more resistance = less current.
 

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Discussion Starter #19 (Edited)
That is what I said. True if Voltage is constant but in context I was refering to comparing DRL voltage of 6.25-7.15 volts and 12.5-14.3 Volts on low beam and how current doesn't increase linearally because resistance or impedance in this case increases with heat and voltage. So R in this case has a +c in the formula I=E/tempcR. c being a positive temperature coefficient.

In other words if you double the voltage from 7.15 to 14.3 you don't double the current. It actually only increased by less than 50%.

By the way fuse is still holding.....
 
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