Have just ordered some H7 LED bulbs and when they arrive, want to test them before fitting. Can anyone confirm the polarity of the 2 pins used on an H7? Thought I had discovered the answer on a google search with the attached showing the pin adjacent to the 'flat' surrounding plate is the positive. However, the very next photo I looked at, shows the exact opposite! 😢

Hi Stephen, the short answer I don't know. The thing is you will do no harm if you connect them the wrong way, LED's only conduct in one direction and act just like a regular diode in the reverse direction. So if you put 12V on and nothing lights up then just swap the wires over. 😀

with all car LED bulbs they either come on or they don't if the don't, just reverse the polarity you started with

if they don't come on after that they are not powered up or are broken

usually the utter mind---- is how to fit then - till you realise the little ring twists off - and they come apart in ways no others ever did

 

7 minutes ago, Botus said:

with all car LED bulbs they either come on or they don't...

Guess you missed the post before yours 

Is it definite that these bulbs are polarity sensitive? If there's no polarity indication on the pin base could that imply they're fitted with integrated diodes - a full-wave rectifier - which would mean they can be fitted either way round.

1 minute ago, mjt said:

...which would mean they can be fitted either way round.

They physically can only fit in an H7 holder the one way, so standard halogen just 'work' though I believe that they would also still light even if fitted round the wrong way! I was only asking about the LEDs as I was just going to bench test them before fitting and didn't want to damage them... 

I know they can physically only be fitted one way round. What I really meant was that maybe there is no restriction on which way round the socket is wired. I'm not even sure whether there is a standard for this in cars designed for halogens which would mean that polarity sensitive bulbs might not work in some makes/models.

its possible they can have enough brains to sort it - but most are cheap and the pack just says try it - if not working swap them around...

 

The polarity of a H7 bulb is not mentioned in the relevant standard (ECE-R37).

H7 is a standardized halogen bulb on which polarity does not matter. The filament will light up regardless of the direction of current.

Since the polarity is not standardized every car manufacturer can have their own interpretation of the polarity of the H7 connector. This can be a problem when installing LED bulbs inside headlights where the H7 socket is part of the bulb locking mechanism and the polarity needs to be changed. 

My experience is that H7 LED bulbs with a decent light output generate quite a lot of heat. These require to be actively cooled (fan) or passively cooled (large heatink). LED bulbs without any cooling generally have quite a low light output or do not last very long.