Headlight Bulbs
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Thread: Headlight Bulbs

  1. #1
    MIGWeb User
    Join Date
    Nov 2000
    Reading, Berkshire
    1380 Mini and Focus

    Headlight Bulbs

    Last night I replaced the bulbs H4 headlight bulbs in my cav Gsi because the headlights looked a bit dim.

    When I removed the existing bulbs I noticed one was a 90/100 watt and one was an 80/100 watt (both of which I think are illegal for road use).

    I replaced them with some standard Phillips 55/60 watt bulbs.

    The lower wattage bulbs are considerably brighter than the old higher wattage ones. Why would that be???


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  3. #2
    Dom is offline
    MIGWeb Moderator Dom's Avatar
    Join Date
    Sep 2001
    73bhp MK4 Astra POS
    Could be a couple of reasons :

    Headlight bulbs can get dimmer with age - especially the high powered ones. The extra heat can discolour the glass over time leading to reduced light output.

    More likely - the extra current drain from the higher powered bulbs causes a higher voltage drop in the cable feeding them - double the wattage and double the voltage drop. Its pretty typical to lose up to 2-3 volts in the wiring to the bulbs with normal wattage bulbs - put a 100 watt bulb in and you're almost down to half voltage with some wiring.

    I run Osram Silverstar bulbs in the missus fiesta (55/60 watts) and they are much brighter than the standard 55/60 watt bulbs in the cavalier. This is due to the increased xenon gas in the bulb causing the bulbs to glow a lot brighter.

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