Wonky operating headlights. Bizzare and strange.

**davidsonsm** · 2nd November 2013, 09:06 PM

I have to confess to having the illegal bi-xenon kit fitted from hids4u out of the UK. They've worked fine and have been brilliant. And I've been very conscious of lighting up the rear view mirror and the bald head of the cars in front - but quite simply, haven't been as far as I'm aware.

However, I now have a situation where the left dipped beam isn't working and the right full beam isn't either. The left full beam does work.
I've checked voltages the lights and I'm not getting any. I've plugged in my old halogen h4 bulb and that doesn't work either.

Does all of this point to an issue with the becm?

I'll check the voltage output from the becm as well.

P38's are like squeezing a baloon.

**benji** · 3rd November 2013, 12:55 PM

Or wiring. Obviously a dmm wont read the voltage at a hid bulb as its to high.

Yes, if you haven't got voltage at the becm plug then you've got problems. I wonder if the ballast resistors for the hid have a high inrush current; not sure if the relays in the becm would like that.

Do you get any messages on the dash?

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**davidsonsm** · 3rd November 2013, 05:29 PM

Yeah the dash is telling me what's wrong. So the becm is picking up the problem. Had to be becm related wouldn't you say. Originally it was the dipped beam on the right that wasn't working, but that righted itself at the expense of the left.

**Hoges** · 3rd November 2013, 07:15 PM

Originally Posted by davidsonsm

Yeah the dash is telling me what's wrong. So the becm is picking up the problem. Had to be becm related wouldn't you say. Originally it was the dipped beam on the right that wasn't working, but that righted itself at the expense of the left.

sounds political

**johnyrover** · 6th November 2013, 01:38 PM

P38's are like squeezing a baloon.[/QUOTE]

ringo · 6th November 2013, 04:24 PM

Sounds like the BeMC thinks the bulb is burned out. Take a look at this link, in the middle of the page is a modified schematic that should eliminate this type of trouble. I hope it helps.
Range Rover P38 Maintenance repair improvements and tips learned by experience by ownership.

**davidsonsm** · 24th January 2014, 01:04 PM

I've narrowed my headlight problem down to the BeCM. I'll take it out and look for any obvious issues, and give it a good clean. Two questions I'd like to solicite help with:

if I can't cure the problem using my usual hamfisted approach, is there somebody in Australia (preferably Melbourne) that can work on the PCB's?
if I do spot a faulty relay or power transistor (MOSFET), can you still buy them and where?

Mine has just hit that 15 year old stage. It seems like everything I've read about is coming true. I used to read with interest the misfortune of others. Now its Nora's turn.

Best regards - Sean.

**wayneg** · 24th January 2014, 06:31 PM

Out of curiosity were you getting a bulb out warning whilst the Hids were still working correctly. Did you have a Complete plug and play kit or one where you had to add a separate loom
If you can get access to diagnostics you can test each lamp individually, not sure what that would prove if they did all light up but would at least show the wires were all intact.

**davidsonsm** · 24th January 2014, 07:44 PM

Wayne, its definately the becm. I've traced voltages all the way thru. I get the same result if I sub the H4 halogens back in. When the HIDs were working there was no error message. The HIDs came complete with a control box (ballast? ) and wiring that was compatible to just "plug and play". But as was suggested earlier, maybe the inrush current had led to the demise of a power transistor. Somebody out there must have a drawer full of them.

Anybody tried the LED headlights?

I might try and get a spare BECM for spare parts. Just need the part number for mine.

**Hoges** · 24th January 2014, 10:46 PM

Originally Posted by davidsonsm

Wayne, its definately the becm. I've traced voltages all the way thru. I get the same result if I sub the H4 halogens back in. When the HIDs were working there was no error message. The HIDs came complete with a control box (ballast? ) and wiring that was compatible to just "plug and play". But as was suggested earlier, maybe the inrush current had led to the demise of a power transistor. Somebody out there must have a drawer full of them.

Anybody tried the LED headlights?

I might try and get a spare BECM for spare parts. Just need the part number for mine.

The electronic industry identification part numbers for the BECM power transistors are BUK202-50Y and BUK203-50Y.

It's been a while since I got enthused over these... they are critical to the BECM obviously

and in a similar category to the crankshaft position sensor as regards being a "show stopper" if they fail. Thankfully, provided there's no undue current demands made on the BECM, they are highly reliable.

The not-so-good news is that these particular power transistors appear to be no longer manufactured and certainly not available for purchase in small numbers. However, other posts in rr.net and IIRC on here, indicate that they have been superseded and that the updated MOSFETs can be substituted.

Rupert Prior on this forum is most knowledgeable on these matters (i.e. the secret life of BECMs!) and may be able to assist.

I haven't had the need or desire to examine my BECM intently. If the BECM electronic components have been assembled using so-called "surface mount technology" then replacement of the MOSFETs will require a delicate touch indeed with a soldering iron and lots of know-how...

Thread: Wonky operating headlights. Bizzare and strange.

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Wonky operating headlights. Bizzare and strange.

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