Rep Power: 297

Hi,

I got ebay fog light kits and installed.

Somehow the lights do not light up! I have multimeter and I got 12V reading right at the socket of the bulb. That means I didn't screw up anything, 12V reached the bulb.

But it can't light up!! why???

The only thing I can think of is that the cheap ebay wire harness reversed the + and - right at the bulb socket and since the H11 bulb is made that it can only be plugged into the socket one way (can't reverse it); I start to ask myself, does H11 bulb has polarity??

I thought the bulb has no polarity...am I wrong?

ANyone knows??

 
Rep Power: 435

afaik, halogen bulbs have no polarity. just make sure you have a positive and a ground and it should light up. there was a thread a few days ago where the user ended up having to rewire a new relay into his harness cause the old relay was dead. check into that.

 
Rep Power: 297

That is extremely strange.

The relay is definitely working, because I hear the click sound and after click, 12V from battery goes right to the other end, reaching the bulb socket.

As I said, I got 12V right at the bulb socket, plug in the bulb and it does not light up.

PS: the 2 holes of the socket, while probing with the multimeter with red and black end, shows 12V.

The fact that the bulb does not light up is strange to hell.

any other thought??

 
Rep Power: 320

u needa check for voltage drop out the ground...cuz you can get 12 volts going in but if the bulb is bad than you will get a voltage drop of 12 at the ground

 
Rep Power: 786

maybe the bulbs are no good

 
Rep Power: 297

I tested 3 brand new bulbs...the filement looks fine.

So the verdict is htat there is no polarity?

So it has to be the socket!! maybe when bulb are plugged in the male and female ends does not even contact each other!

 
Rep Power: 435

^that was going to be my next suggestion. check to see if the bulb filament is dislodged/broken/burnt/not there.

edit: nevermind. have you tried running 2 wires directly from the battery to the bulbs? maybe a bad idea, but hey, you're already at step 0.

 
Rep Power: 297

yeah, that is my next step.

I will go to office tomorrow and use a power supply to test it.

So we are all sure there is no polarity difference? so I can apply +12V to either pin of the bulb?

I work in high tech, that is why so ashamed and pissed that I can't figure out why bulb would not light up when I got everything worked out on paper before installing everything! god damn it is just DC ohm's law!

 
Rep Power: 435

it could also be KVL at play. what goes in must come out...

 
Rep Power: 297

HI,

It ends up being rust between different points of car chassis. A bolt that is fixed to the chassis of the car can be a GND so does a bolt at somewhere else. However, there can be rust in between them, thus act as resistance.

The multimeter tells that there can be discontinuity or resistance between bolts that are fixed on the chassis, it is not reasonable on paper, but when rust is present, it is possible. Honda OEM fog instruction assumed the car is brand new so no dust or rust are present.

I modified the OEM foglight harness so that both fog lamp's GDN are connect to one single bolt, I added the size of the wires and I used sand paper to eliminate rust. This way, I got the thing to work.

Conclusion, the car chassis is all metal alright, but with oil/dust/rust mixture, not all point on the chassis can be assumed to be a perfect ground.