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100W bulbs....ooops....

2045 Views 6 Replies 5 Participants Last post by  Ian D
I bought some "Xenon White" bright white bulbs on ebay to replace the park lights, fog lights & high beams on my XJR to match the factory Bi-Xenons (i don't need to tell you, how terrible it looks with the mix of yellow and white lights).

Gots H3's for the fogs, 55W with a free pair of W5W 5W for the park lights.
H7's for the high beams, but didn't realise that they were 100W instead of the usual 55W...!

Will this be a problem for fuses? I can't imagine it'll be a problem from the inspection, when the flap in the Bi-Xenons opens for high beam it's totally blinding, and you can barely notice the high beams in the inner lamps anyhow.

Anyone fitted 100W high beams before? Any problems?
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I fitted Osram 50% brighter (55w) and drove around with day running lights on for a while.

I found that the plastic connectors onto the spades on the bulbs were overheating and degrading

due to heat being transmitted along the spades. (I assume)

I now have ceramic connectors to fit onto the bulbs (ex Hong Kong via e bay).
Thanks Rob. Although i wasn't so much worried about the heat (the high beams get very little use in comparison to low beam).

Just hope they don't blow any fuses or give CANBUS errors....
I would be getting some relays out matey you don't want to fry your wiring! You can use the resistor approach across the relay if you get an error. Unlikely for main beam.

How does the Swiss MOT test fair with higher rated bulbs? Not the modding owners friend so I hear.
I'm less worried about the MFK (Motorfarhrzeugkontrolle) since;

- Is it even a legal requirement that a car has high beams? It's not like they are really needed is it?
- The Bi-Xenons are so bright on full-beam, the standard 55W high beam at the moment is hardly noticeable.

I walked in front of the car with the high-beams on after i changed over the flaps and i had grey spots in my vision for a couple of hours afterwards. If the inspector even notices the 100W bulbs in the inner lights, then hats off to him!

Fry the wiring? Yes that's a concern, or at least blowing going by the numbers;

12V 55W bulbs would pull 4.58A at 12V.
But in reality it's more like 13.8-14.4V, so that would be 3.82-3.98A with the 55W.
100W bulbs at 13.8-14.4V would pull 6.95-7.24A.
The fuse for both left & right main beams lights together is 20A (F16, under the bonnet)
Even at 12V, both bulbs together would only pull 16.6A, at another 0.5 for the resistance of the wiring (worst case) and it's still under the 20A.

So why is there a 20A fuse in place, when the standard 55W bulbs together would only pull a max of 8A?
Might be for the inrush current when the bulbs first turn on....?

As you can tell, I know just enough about electricity & electronics to be dangerous....:D

The CANBUS measures the resistance of each light circuit, & if it's too low then it thinks the bulb has blown & you get the message.
But what happens if the resistance is too high? It won't be a problem while the bulbs are cold (regardless of wattage, they all pretty much have a 0.5Ω resistance when cold) but when they warm up, will it realise there is too much resistance or current & give me an error message?

And the wiring...if a wire can take 4A, it can take 8A, for short periods, again it's not like high beams are on all the time...

In any case, i'm not running the lights until the test, just in case the superglue melts...;)
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I once put 100W bulbs into a car I had years ago and after a while it burnt out the headlight switch but so be careful.
I remember having 100w bulbs in one of my previous cars and because the headlamp lenses were plastic it began to melt hotspots. Ruined the headlamp!
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