Is it not possible run a feed directly from the battery for Hids via a relay. Then put a resistor across the normal bulb connection of a similar value to the 55w bulb?

This can't be the correct calculation surely?

 

My electrical calculation knowledge is very faded in the back of my mind

 

H7 55w bulb at 12v is 4.58 amps

 

V= IxR or V/I = R

 

12/4.58 = 2.6 Ohms? Surely that wouldn't be enough?

Those numbers are about right the trouble with dissipating 55w in a resistor are that you end up with what is basically what amounts to a small electric fire under your bonnet! (all be it insulated in ceramic), and a 55w resistor is huge! e.g. this one is 4.5inches long!

 

http://www.tedss.com/2021011414

There are two repair procedures that I'm aware of, one is to replace the mosfet completely, the other is to remap the function of the damaged channel to a spare channel and switch a wire over in the plug. From what I understand, there is only one spare channel and it might not be viable depending on the original damage.

 

Easiest way to tell is from a VCDS autoscan, it'll be listed under Address 09: Cent. Elect. (J519).

 

Otherwise you could look at the module, it lives above the pedals in the drivers footwell. You'll probably need to remove trim to get at it but with a borescope you might get away with it. Should have a lovely big sticker on it like this:

 

Thanks for this. Do you have any more detail about the damaged Mosfet. Is it just the one shorted transistor or does the damage go further? Any links to repair details you know of?

Thanks for this. Do you have any more detail about the damaged Mosfet. Is it just the one shorted transistor or does the damage go further? Any links to repair details you know of?

Sure, hope your Russian is good: http://forum.skoda-club.ru/viewtopic.php?f=99&t=89544

 

I used google translate to get an idea of what's happening. The mosfet used is something similar to this http://www.st.com/web/en/resource/technical/document/datasheet/CD00151721.pdf but I think it may change slightly between revisions.

Thanks the translate option does indeed really give only an idea. Those mosfet chips are only a couple of quid, assuming the similar ones in our BCMs are also similar prices, so certainly worth a go to change it for anyone with a duff unit. Anyone with a duff unit want to give it a go?