As the previous thread went a little off topic, I thought I'd start a new one to try and get answers.

I'm keen to get HID's (obviously) before winter kicks in, when headlights are needed for every journey 

 

As per this thread, and with help from softscoop, mikeholroyd, langers2k, paddypaws. It LOOKS like there may be a harmless way of fitting HID's without endangering the BCM.

 

I would like someone with more electrical knowledge than me to advise whether using this Relay Kit would work, and with no risk to the BCM? Would I need anything other than this?

Also, would anyone know whether any coding would need to be done to the car to let it know about the HID's, I wouldn't expect so?

 

I have zero electrical knowledge so any help is appreciated, as ever.  :beer: 

 

With the resistors fitted, they are probably close enough to emulate a halogen bulb so avoid the bulb warning. Given this, they shouldn't need coding either..

 

Just be warned those resistors will get hot so need attaching to something big a metal that won't get damaged from the heat.

 

Assuming they are correctly fitted, I really can't see any risk to the BCM.

Why would coding for any module need coding?

Your using from the battery,and just a signal/switch from a live feed.

 

I'd say that would be pretty safe.

 

I have done this on quite a few 4x4 for off road spot light's.Led bar's ect.

 

Not sure why you will need resistors?

 

Am i getting the wrong picture?

Why would coding for any module need coding?

Your using from the battery,and just a signal/switch from a live feed.

I'd say that would be pretty safe.

I have done this on quite a few 4x4 for off road spot light's.Led bar's ect.

Not sure why you will need resistors?

Am i getting the wrong picture?

Basically CAN BUS.

I just remembered Pre is CECM and facelift is BCM 

So essentially the wiring loom mimics the resistance produced by the halogen bulbs, fooling the car in to thinking the old bulbs are still in place?

If it successfully does this, then I can't see a reason why this would not work, or why any coding would be needed.

 

Someone please correct me if I am over simplifying however.

So essentially the wiring loom mimics the resistance produced by the halogen bulbs, fooling the car in to thinking the old bulbs are still in place?

If it successfully does this, then I can't see a reason why this would not work, or why any coding would be needed.

 

Someone please correct me if I am over simplifying however.

 

Entirely correct, as I stated in post 3

 

Will the 50w resistors in the loom be enough to fool the car, or would you recommend some other way to do this?

And where would you recommend mounting them?

 

Be aware that the plugs to go onto the bulbs would have to be cut off and spade terminals added as the ones on the plugs supplied (female 9006) will not fit the H7 bulbs needed for dipped headlights.

 

Which plugs would be needed? Or is spade terminals the only way to go?

I would expect the resistors are close enough to halogen bulbs to fool the BCM. It is there only purpose

 

I'd attach them to any decent sized piece of bodywork, avoiding the inside surface of any exterior body work. Mostly to make sure the heat doesn't effect the paint work or any wax etc. There is plenty down and around the rear/underside of the headlight area.

Would you not choose to code as for HID and put a smaller resistor in (if any - is there a bulb/load check if HID is coded?)

 

You are already taking out the potentially risky route of connecting HID ballast to BCM by using the relay. I would probably try to avoid adding in a couple of '50W' resistors if possible!

Why not just use a loom,and buy the "error resistor's" that plug inline...Most HID kit's come with them anyway?

The annoying thing about forums is the people that cloud the issue with comments that are unhelpful because they haven't read and understood the thread from the beginning.

 

Would you not choose to code as for HID and put a smaller resistor in (if any - is there a bulb/load check if HID is coded?)

 

You are already taking out the potentially risky route of connecting HID ballast to BCM by using the relay. I would probably try to avoid adding in a couple of '50W' resistors if possible!

He isn't connecting the HID ballast to the BCM that's the whole point of the thread, he's connecting to the battery via a relay that will be triggered by the BCM. 

 

 

Why not just use a loom,and buy the "error resistor's" that plug inline...Most HID kit's come with them anyway?

The supplied 'Canbus error fixers' that come with HID kits are capacitors not resistors. Not the same at all, they fool the BCM that the load is a normal filament bulb by having a similar high initial load which tails off to become flat like a filament bulb.  That's completely different and will cause BCM damage in the medium to long term in many VAG cars with BCMs.

 

 

 

 

This relay method may not work because the relay coil may cause a voltage spike on switching just like a HID ballast may do. A ballast may put A.C. ripple on the BCM output in addition.  I think the safest solution to protect the BCM is a schottky diode in series and diode in parallel to kill any back emf spikes (reverse polarised). This should isolate the BCM. Most relays should be internally protected, but better to be safe than sorry. You'd still need to code for HIDs.

Edited 20 September, 20169 yr by paddypaws

The annoying thing about forums is the people that cloud the issue with comments that are unhelpful because they haven't read and understood the thread from the beginning.

 

He isn't connecting the HID ballast to the BCM that's the whole point of the thread, he's connecting to the battery via a relay that will be triggered by the BCM. 

 

The annoying thing about forums is the people that cloud the issue with comments that are unhelpful because they haven't read and understood a post properly..

 

I suggest you re-read what I said (but if you still have any difficulty, 'taking out' means removing.)

This relay method may not work because the relay coil may cause a voltage spike on switching just like a HID ballast may do. A ballast may put A.C. ripple on the BCM output in addition.  I think the safest solution to protect the BCM is a schottky diode in series and diode in parallel to kill any back emf spikes (reverse polarised). This should isolate the BCM. Most relays should be internally protected, but better to be safe than sorry. You'd still need to code for HIDs.

 

Would the supplied resistors not be a safe way to fool the BCM? Isn't that their only job  :peek:

In that case don't be tight and do it properly.

Xenon retrofit.

Job done 

The relay kit I have linked specifies 2 x 50W 8 ohm Load resistors