P38A No main beam l/h side

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dh-t

dh-t

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37
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bolton by bowland
Hi there ,my problem is that when I switch to main beam only the right hand side goes to main beam,the two inner lamps also go to main beam.I have changed over the bulbs but still no joy.The bulbs are 100\80 12v ,should I go to 55\60's ,would that make any difference?. I can't find anything wrong with the wireing .Anyone got any ideas?.
 
100/80 bulbs are strictly speaking not for road use from memory....but anywho....

If the lamps are switched via the BeCM....and the BeCM has the power MOSFETS (or whatever they are called) in that controls the outputs to the lamps, then the higher wattages *may* have fried the power circuits within the BeCM.....I say *may*/*could*/*might* as I don't know....Rick-the_Pick or MartyV8 will know more no doubt....
 
Use a meter and check you are getting 12 volts to Blue/Black tracer wire on pin 1 and Blue/Pink tracer wire on pin 2, don't know which is inner and outer so check both when full beam is selected. Headlamps are switched by the BECM. Check grounds on pins 6 and 3. Hope you haven't smoked the switching transistor by using wrong bulbs.
 
Do you get a bulb failure message on the dash, along with the lamp not coming on?

It is entriely possible the MOSFET has been cooked by running at higher capacity than what it is rated for - or it could be possible the MOSFET is OK, and it's burnt the track through on the BECM (if it isn't a socket or wiring in the vehicle loom issues).

The tracks are repairable usually (the bigger ones are pretty easy to do) and the MOSFETs are also replaceable.

I'd personally switch back to 60/55 lamps as that's what the electrical system is designed for.
 
martyuk said:
Do you get a bulb failure message on the dash, along with the lamp not coming on?

It is entriely possible the MOSFET has been cooked by running at higher capacity than what it is rated for - or it could be possible the MOSFET is OK, and it's burnt the track through on the BECM (if it isn't a socket or wiring in the vehicle loom issues).

The tracks are repairable usually (the bigger ones are pretty easy to do) and the MOSFETs are also replaceable.

I'd personally switch back to 60/55 lamps as that's what the electrical system is designed for.
Click to expand...
 
Thank you,I have changed back to 55\60 lamps ,the car is booked in for next week to be checked over prior to MOT'd , Are the MOSFET's easy to change if that is what it turns out to be,and will my local Land Rover engineer know what to look for.
 
dh-t said:
Thank you,I have changed back to 55\60 lamps ,the car is booked in for next week to be checked over prior to MOT'd , Are the MOSFET's easy to change if that is what it turns out to be,and will my local Land Rover engineer know what to look for.
Click to expand...

The 'metal oxide semiconductor field-effect transistor' can be replace but easer to replace the whole board.
Will your local LR engineer know what to look for? if he's also a qualified electronics engineer which I doubt but if so Yes.
 
discool said:
The 'metal oxide semiconductor field-effect transistor' can be replace but easer to replace the whole board.
Will your local LR engineer know what to look for? if he's also a qualified electronics engineer which I doubt but if so Yes.
Click to expand...

All he has to do is check the output from the BECM is zero. Plug in diag, try to switch lights on, if still output = 0 then open up the BECM and look for cooking. Most mechanics would manage that, I think. Replacing the MOSFET might be trickier.
 
Grrrrrr said:
All he has to do is check the output from the BECM is zero. Plug in diag, try to switch lights on, if still output = 0 then open up the BECM and look for cooking. Most mechanics would manage that, I think. Replacing the MOSFET might be trickier.
Click to expand...

Errr ... Read and understand the two questions the OP placed... will they know what a MOSFET looks like if that componant is faulty I doubt it.
 
Last edited:
There's just over 30 MOSFETs and a couple of other transistors/voltage regulators on the power board. They aren't hard to change - but it can be easier to just swap the power board (or in fact the logic board into another BEC housing as the power board/fuse box are bolted to the studs in the BECM, so swapping logic board is quicker. As long as it's the same either high line/low line BECM board, then it should work fine.

Don't let them tell you they need to swap the whole BECM/locks/ignition/remote etc as that ends up causing more headaches than it's worth.

Failing all that, I'm back home in a week or so's time - I'm happy to replace the MOSFET/repair the power board if that's where the problem is. I have spare MOSFETs sitting on the shelf
 
MOSFET's, now there's a stroll down electronic memory lane :D

I remember when MOSFET amps were all the rage :rolleyes:
 
Would I be able to splice into the inner main beam and run a line to the main beam pin on the outer dip / main beam light ?. If the bulbs are 55\60 would that work or maybe overload the mofset.I ask in case the garage is unable to sort out the problem without going down the becm removal route.
 
Don't know what rating the mofsets are but as it sounds like a 100w lamp has fried one, I wouldn't do it.
If the only option is to frig the wiring, add a relay into the circuit that's fired by the working headlight and wire the non working bulb to that from a fused battery feed.
Personally I'd want it fixed properly.
 
Wazzajnr said:
Don't know what rating the mofsets are but as it sounds like a 100w lamp has fried one, I wouldn't do it.
If the only option is to frig the wiring, add a relay into the circuit that's fired by the working headlight and wire the non working bulb to that from a fused battery feed.
Personally I'd want it fixed properly.
Click to expand...

Plus one.

Car fires happen...
 
Well thanks for all the replies, the car went for MOT yesterday at Ribblesdale Land Rover ,passed OK no advisories ,they fixed the main beam,faulty connection on the main beam circuit ,so happy happy days. Ribblesdale provided me with a Defender for the day and on collecting my car it had been valeted.Now that's what I call service.
 
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