has anyone fitted LED H4 globes. i have acquired a secondhand set with no instructions!
I haven't, but you'd have to expect that if they're H4 replacement globes, then they should just fit straight in.
I'd be interested to see how they go in some of the newer cars. There's an issue with the way they manage power to the headlight globes.
The issue is that in the traditional H4 setup, you have a "U" arrangement of tabs that accept power. The left side of the "U" (as you're looking at the base of the bulb) is the "Common" which used to be connected to negative. The bottom of the U is low beam, and the right hand one is high beam. We'd tap into that right hand one for a positive feed to a relay for driving lights and it'd work.
In newer cars, that's not necessarily the case. The "Common" pin might be negative on low beam, but it switches to positive on high beam with the high beam pin changing to negative. I tried fitting a relay to one of these cars and ended up connecting pin 85 to common and 86 to high beam just to get the things to work!
Now this will make the LED thing interesting - because LED is a diode, it only accepts power one way. If you try to power it backwards, you could burn it out at worst - so I expect cheaper LED units to fail in the newer setups.
My advice with LED units: check how your headlights change from low to high beam and if they're on the "new" method, there's some advantage in either carefully purchasing LED globes, or using a pair of relays to change the "new" H4 back to the old H4.
And a word on LED emitters - if the actual light emitting element of the globes isn't in the same location as the tungsten filaments in the halogen globe, the light will be created in the wrong place and won't be focussed correctly to shine forward well enough. This will not only weaken the amount of light available to you, but could easily cause a great deal of glare for oncoming drivers.
And causing the driver of a car coming towards you to be unable to see ... not really very high on the clever scale.
