Info on halogen bulbs please

[meyrick]

Hi,

I'm in the process of replacing my tungsten unit with a halogen one via relays etc. and I'm a bit puzzled by the new bulb (it's a 55/60 P43T by the way). I was trying to figure out which pin was for high beam and which for dipped beam and I am still none the wiser. The thing is, according to my multimeter each of the three pins is connected to the other two by almost no resistance (~1ohm). That can't be right can it?

So I guess my questions are:

1.) Which pin is high and which is dipped and should they be + or - (I'm assuming the other pin is a common + or -).

And:

2.) Is my bulb buggered? What's with all the pins being connected to each other?

The bulb looks fine on inspection, it's not blown and I bought it this morning. Help me get back on the road while the weather's still good!!! Cheers

[Fortuna]

OK here goes,
I don't have the pin out but will search for you.
Yes less than 10 ohms is correct as the filament is metal and therefore a good conductor. As it has a low resistance a lot of current can pass through lighting it up.
On a halogen lamp there will be one ground and two live feeds (dip and main).

[meyrick]

[meyrick]

I just went into the garage and tested the bulb inside the headlight unit to determine the pin out. As it was such a pain, here are my findings for any who may need them in future:

Assuming you are looking at the back end of a P43T also known as an H4 halogen bulb...

[Fortuna]

[meyrick]