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2015 SLK55 AMG
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Discussion Starter · #1 ·
I have done this conversion on two Subaru's and a Mazda,with no difficulty.
They had Canbus.
I have just tried an install on my 2012 SLK350 and had to revert back to the H7's.

Initially both HID's worked OK and the improvement is huge, as it always is.
After about a 20mins drive the first one turned off. I stopped and restarted and then neither would come on.

The status display informs me RH and LH Dip Beam are out.

So back in the garage I checked out the two units in situ, with DC from a seperate battery and they work normally.

I dont understand why it worked at all in the first place.

The web is full of comments on Canbus and how to fix it with a 4700uF Capacitor (I tried it and it made no difference).

What I could not find is any technical discussion on how the lamps are monitored, and how Canbus turns them off. Given the H7s draw about 4.5A and the HID is 4.3A it should not see any problem. The peak current at turn on is higher at about 7A for the HID.

Does anyone understand this well enough to explain what is happening ?

I assume someone has managed a successful install - if so what kit did you use ?
 

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you have to find a shop or members that have DAS/STAR to do it for you :D
I am sure members will jump in that can assist you
 

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Based on what Audis do, the xenons take a BIG power input to get them going then they only take a fraction of the power the halogen bulb does. The reduced power usage fools the car's monitoring system into thinking the bulb has failed and to save needless power output, it shuts down the headlamps. The issue isn't just that the car is using the CANBus, it's also using PWM and that isn't fooled by the addition of a capacitor or resistor into the circuit. So you need a PWM compatible CANBus compatible kit.
 

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Discussion Starter · #6 ·
PWM - If you mean Pulse Width Modulation - of what ?
The supply to the H7 is DC at nominal 13.8V, its not a PWM supply.

As I said in the first post the Peak current draw for HID is about 7A, (I have a DC Current clamp with Max Hold) the H7 are about 6A. After about 15seconds the HID is slightly less than the H7 at 4.3A versus 4.5A , hardly significant.

However the car is clearly able to tell its got something other than an H7 connected, maybe its the rate of rise when turned on.

I will see a local MB indy tommorrow and see if they can set xenon=present
Then put the kit back on.
The improvement is so good its worth persevering.
 

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It is PWM. Why do you think 13.8V DC can't be PWM?

Why do you think the CANBus 'fix' is a capacitor and not a resistor? The idea behind the capacitor is to eliminate the PWM effect.

There are various threads about building PWM filters to get xenon retrofit kits running on PWM halogen equipped cars.

They use PWM to eliminate the need for heavy additional circuitry and easily worn variable resistors in the multiplex wiring loom. It also extends the life of incandescent bulbs.
 

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Discussion Starter · #8 ·
To close this off, job done and its working OK.

All the talk of Canbus errors is a Red Herring, the underlying problem is most of the HID inverters draw a higher peak current when first turned on than an H7.

The SLK is measuring the current when loads are turned on with a Hall effect sensor on the Battery Terminal, so when the low beam is turned on and it senses a much higher current than it expects (i,e possible short) it turns it off, either permanently or it cycles. This is where the "Capacitor Fix" comes in, it doesnt cure it, it just keeps the inverter running in the "Off" periods, this will likely generate a lot of RF inteference as well as a lot of stress for the switching device that is continually recharging the (4700uF - big) capacitor.

So what you need is an inverter (ballast) that limits its current to the same as an H7 inrush at turn on. The unit I have has a maximum current of 3.6A and it runs at a steady 3.2A. Cost £28 with H7's on ebay from UK.

Lights are now much better than standard.

I read a number of comments about the focal point of HID lamps, if you hold one next to an H7 the discharge point is exactly in line with centre of an H7 filament so it should be in focus, and looking at the beam pattern on a wall it is crisp and well defined.
 

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Discussion Starter · #10 ·
Because these things are sold at anything between £15 (from China) and £50 (from UK seller) and they all have varying degrees of flannel about how good they are, I'll put up a picture of the one that didnt work and the one that did.

The one that didnt work looked very nicely made, but when I looked at the current it drew using a shunt and my Scope the current spikes were as much as 50Amp and coming thick and fast, continuing after warm up as well.

The one that did work in contrast clearly had circuitry that was controlling the inrush current, it rose to under 4Amps and then gradually dropped to 3.2A.

So it works, or doesnt cause (valid) errors because it mimics the H7 load characteristics.

So all this guff about error cancelling and decoding is pure bs.

So as with a lot of this Chinese stuff it can be very bad or very good, problem is you cant tell one from the other and price is the last thing to use.

Arthur
 

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Hi Arthur, thanks for the info. I found the "black" HID module you said worked listed on eBay, it mentions that "there other items you may need" e.g. bulb holders, did you need any additional items for your install? + how difficult was it, what was was involved.. any pictures?
 

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Discussion Starter · #15 ·
When you get the units run them on the bench for an hour with the bulbs in a metal box so you dont accidentally look at them.

I have had a few Dead on Arrival pieces of kit from China, its easier to do this than strip it out when it doesnt work. Also most electronics with build faults will die early on if they are going to fail otherwise they tend to last forever.

The other caution is that buying one that looks the same is no gaurantee that it is the same !

Having said that I have ordered a spare set from China to leave in the boot, at the half the price of the UK one, different brand and wild claims, designed in Germany, approved by NASA etc !

The job takes about an hour each side.

Remove the plastic trim, it has two plastic rivets, see picture.

Despite the user manual saying bulbs can be changed by turning the wheel in, I wouldnt try it.

Take the wheel off and slide up the hatch cover in the wheel arch liner to get access to the back of the bulb holder.

A Head Torch is worth having, you need a clear view of the parts.

Turn the big round cap acw to reveal the H7 holder.

With the connector still on the H7 slide the spring clip upwards (it doesnt come off) pull the bulb out, remove it from the connector.

The round cap needs a 20mm hole drilling in it to take the grommet.

To pass the 2 pin power plug through the hole you need to back out the pins and take them out of the shell, Mark + and - on the shell before, a jewellers screwdriver poked in releases the latches. Reassemble when passed through the hole.

Back under the wheel arch fit the HID bulb, this is fiddly.
Connect the power leads, polarity matters so check for the positive (I use a test lamp with one side to ground) and put the cap back on.

The pictures show where I located the Inverter, its under the Stanley Tape Measure held by one tyrap.

The cable routing is common sense, keep them away from sharp edges etc.
Restrain the Transformer Block with another tyrap so it doesnt slide around.

To be sure they are not going to play up I would drive around in the day with them on for a few hours (like most people seem to today !)

I have used mine for about a week with no problems, its a big improvement.


Arthur
 

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Got mine installed ! and happy to reports it works and looks great . much improved visibility .. and no code on the dash and they don't turn off ... installation however was a PITA . I have bruised forearms from wrestling that clip into place ... the rest was a breeze ... but at some point i thought i would never get those clips back in .. you definitely need patience and small hands .. I have neither! i had to stop and try again at least a dozen times , but finally got them in...
 
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