Are you using "4" 100 watt lamps for the high beams? If so then you need 15
amps not counting the in rush of starting cold bulbs. Yes check the
resistance of a bulb at room temperature and use ohm's law to calculate the
current. 14 gauge wiring for each set, 12 or even 10 gauge to battery. I use
20 amp circuits for each side. Don't forget to upgrade the wiring from
alternator to the battery cable. Keep spare bulbs and sockets on hand for
long trips. Melt downs and burned out filaments are common with the high
wattage bulbs.  400 watts is about 33 amps out of the 90 max available from
the alternator. High beams with AC or both heater fans and then the radiator
fan can result in overloading the alternator. You may now need to consider
power management while driving. Probably half the bulb upgrades I have done
over the years have been pulled out. Also consider that while you may not
get flashed by oncoming traffic you can be putting glare into vehicles you
follow. Truckers can really get affected due to the high placement of their
mirrors.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
neil n
Sent: Wednesday, October 24, 2012 6:33 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Headlight Upgrade Double Check (fuses)

Hi all.

I'm installing H4 round headlights with 80/100 Watt bulbs. ('88 Westy) I saw
Alistair's diagrams (thank you Alistair!).

Using P = IE at ~ 13 Volts 100 Watts is 7.7 Amps

Stock fuses are 10 Amps each.

I'll run new circuits from the battery to headlights.

Will four 10 Amp fuses suffice for 80/100 Watt bulbs?

Thanks

Neil.

--
Neil n

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'88 Slate Blue Westy to be named.

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