Up grading head light globes

hi all, have been thinking about changing the H1 55w full beam globes for 100w. has anyone done this and did it make much difference?

The better change is if you can source a set of lamps from the X308 drop straight in and much better lights. My Brother did this to his X300.

hi robin, i think i have heard of that somewhere else. it’s just that i have a spare pair of the 100w globes so wondered if it would be any brighter.

I’ve gone with 100W and 130W bulbs on earlier cars a couple of times. Generally the results are disappointing because the wiring in the car cannot handle the load. The increased voltage losses in the leads result in a low voltage at the bulb, and the light produced is barely better than with the OEM bulbs.

But that just inspires me to install headlight relays. Hence, instead of the power for the headlights going from battery to headlight switch to dimmer switch to bulb – all with the lightest gauge wiring the manufacturer thought they could get away with – all that wiring merely activates a relay. I run a new heavy gauge wire directly from the battery to the relay and from there to the bulb – and upgrade the ground circuit from the bulb while I’m at it. Then I get headlights that could melt the rear bumper of the car in front of me!

On my '83 XJ-S, I ended up with four headlights and two driving lights, all six of which were 100W. The driving lights proved to be useless, there was already so much light out there that they didn’t really contribute anything.

BTW, it’s entirely possible your later car already has headlight relays. Manufacturers have gotten smarter since about 1990.

Oh, also upgraded my alt from the Lucas 75W to a CS130. Besides the additional capacity, the Lucas charged at 13.6V while the CS130 charged at 14.4V. The difference in voltage brought the headlights from bright yellow to bright white.

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hi, thanks for the info.

The X300 is a can bus system so the light switch dosen’t carry the load, thats taken by the BFM’s I used 100w in my ‘40 and the lights output did improve

yes i put 75w/100w in my old xj40 with the fish tank headlights and they lit up the road well.

Make sure you get the wiring looms with the lamp units as the plugs are different and you’ll need to splice these in and adjust the connections also see Jim Butterworth’s write up:


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thanks for that neil.

Check thru the archives. I did an upgrade to my X300 by fitting X308 headlights, which required a minor rewire. I also fitted HID bulbs. 8 years later and it passes its yearly inspection and the light is brilliant.

hi greg, ok will look that up. thanks.