E39 high beam stays on !!

High everyone ... I have a prob with my 1998 520I lim . The off side high beam light stays on ALL the time even when the key is out of the ignition. Its not the indicator switch/ parking light thing. I figure that the relay has welded shut... problem is BMW wont even tell me were to look for the relay. with ingnition off and key removed, I've pulled every relay I can find (all in the boot). So can anyone tell me either .. were the high beam relay is (I assume each high beam light has a sepertate one) or has anyone had this prob.... BMW said it might be a wiring fault behind the dash .. at this I exploded .. an efin 6 year old car with a loom fault .. how do they get away with it. They then backed down and agreed that it was prob relay .. but just wont tell me were the blody thing is hidden (and I thought VW ran a  monoploy) ...... cheers anyone !! 

I think Doive is an electrical engineer, based in Edinburgh. He may be
able to give you some advice on repairing the module. Look for him on
other posts and send a PM.

Repairs on electronic modules are fairly easy as long as you know what is likely to be at fault!! Best scenario is to open a board and find a component all surrounded with brown carbonised deposits - thats the one! More often than not something will have failed internally, showing no external faults at all.

For the transistor take the part number of the faulty one to somewhere like Maplin and get a direct replacement, then solder the new one in. One thing it is advisable to do before opening the module is to earth yourself - take off all wooly jumpers or fleeces before you start, and touch something like a radiator or a water pipe in your house to get rid of all static. Often these modules will have been built in a static free environment, so are likely to be fairly sensitive. Toxic sounds like he knows what he is talking about, having done it already so you could ask him the details. Of course if the guys at work are going to have a go at it, leave them to it!

Pete, I sent you a PM of it's location.  Size is about 200mm x 120mm x 40mm.  Black in color with a large heatsink visible on one side.

I didn't notice any visible component failure, just had to trace from the light wire color to the module, to the connector and to the component.  You can verify the resistance across the suspected faulty transistor pins to a known good one jst to verify 100% you got the right one.

A good solder iron & solder sucker is required.  When soldering the new one in, try not to spend too long soldering the pins.  You don't want to damage anything more than you have already.

The guys in work should have it fixed for you.  I actually found trying to remove the module more difficult.  You'll need a socket set and a set of torx bits to remove the module since the bonnet release lever needs to be removed and the panle behind it.  One nut holding teh module in at the bottom of it..I think a 10mm.  after that its just move a wire harness out of teh way and rotate it 90deg to get it out.  3 connectors to be removed, one for left side of car, one for right and one for signals from the buttons & levers in the car.  Best of luck Pete.

Tom

That article is just what you need to show you how to remove the module.  What you see on the first page is the internal of the module with the cover off.

When you get to that stage, you need to remove the heatsink which is the large metal section with all the fins.  I think its secured from the underside.

The lamp I had the problem with was front right headlamp.  I think the wire from the lamp came down to pin 13 of the bottom left black connector.  If you look at the drawing where the sticker with the barcode, the bank of 3 transistors just below it at 4 o'clock, I think it was the middle one or the one to it's right.

You'll probably find the transistor is marked BTS425, made by Infineon.  You won't be able to get these any more.  They are replaced by BTS426L1.  Can be bought at any RS store.  P/N: 354-5893.  They are about €4 each.  I had to pre-order them as they weren't a stock item at my local RS store.

Once you remove the securing screws for the heat sink, there are metal spring clips between each transistor and the body of the heat sink.  Just use a small flat bladed screw driver to prize each one of them out.  You won't be able to get out the heatsink from the board until they are all removed.

What I did, was when I knew the faulty transistor, I snipped the five legs off at the body of the transistor which made it easier to remove each leg once they were being de-soldered.

Yep .. I thought of doing that to get it through it's MOT tommorrow 01 March ... but was worried (little knowledge) 55Watt lamps @ 12 v is a draw current of (been a few years) 4.58amps per buld X 2 = 9amps ..the BTS426L1 is rated @ 7 amps with a current limitation of 16 amps ..I'm not sure what current limitation means ??? . I've ordered the Infineon's from RS and Farnell (to be sure ..ha ha ). And the guy at the garage (not stealers) is gonna try and get it through  MOT by claiming a replacement bulb is required ....fingers crossed.

I'll let you know how I do .and I'll photograph the LCM repair stage by stage.

thanks again for your help and interest