headlight fuse

[vintage bikeworks]

Has anyone found after replacing the stock "candle" of a headlight bulb with one of the modern Sylvania Halogen lamps, that the 10 amp fuse will blow after 10-20 minutes of operation?  The Sylvania replacement is much whiter and brighter and one would suspect it would draw more current.  Wanted to throw the question out there before going to a 15 amp fuse.  Note that I've also replaced the stock glass style fuses with blade type in a new fuse block. 

[QBS]

Been running a 130/90 H4 halogen with a 10amp fuse for many years with zero problems.

[vintage bikeworks]

Thanks QBS.  Will look for shorted wiring in headlight/instrument lighting then. 

[The Prophet of Doom]

I had the same thing on mine when I tried out a high wattage bulb.  The fuse lasted enough for a safety cert and that was about it.
Amps = Watts/Volts so I figured 130W / 12V = 11 Amps, and so pretty borderline for a 10A fuse.   QBS is running OK, so I guess he probably has higher battery voltage, or perhaps a slightly underrated bulb. 

From memory the headlight wire gauge is not that heavy so swapping out the fuse to a 15A puts your wiring at risk.  On my rewire I'm running 2.5mm cable as a minimum for a 15A circuit - which seems to be the recommended width for that current.

[motoracer8]

 The use of a relay will solve hi watt headlamp probblems. 10/11 amps is a lot of current to pass through the tiny contacts in the dimmer switch.

[vintage bikeworks]

Thanks all for the comments.  I checked and the Sylvania "9003 H4 Silverstar Ultra" lamp I used is still only a 60/55 watt and not a high wattage like QBS's.  If you do the math, 60 divided by 12-14 volts should only be a 5-4.3 amp draw, well within the fuse and wiring rating.  Will check connectors and dimmer switch for high resistance and possible chafed wiring.  If and when I go to a 100+ watt lamp, I will definitely rethink wire gauge and a possible relay.  Thanks again.