Don`t know if this is the right place to post it 
What does this sensor do and i notice they is 3 units on the rear of the vehicle near the wheels, i pursume that the value itself is the one where the large spring is on. Does anyone know how it works and verfiy how i can test it before taking it back for the MOT. I would ask my mechanic but they did not spot it when they suppose to check the vehicle over for the MOT. 
When my wagon had load on the cable fasten to spring was lose now taken load of and cable is tightish. Is this right.
hi check this out it may help
A load sensor valve it lets the brakes work more or less depending on the load on the axle.
If you braked with the full brakes while empty you would no doubt lock it up and probably slide.
If you braked when fully loaded with the pressure needed for an empty axle you wouldnt stop!!!.
So i got told it has seize by the mot guy at vosa this is why it failed its mot, but the wagon has worked everyday and loaded or unloaded the brakes work fine to me even when i fully loaded around 8ton they still work fine to me. Like i mention before the spring works up and down when moving it with my hand or is this the wrong part which is seize
Cheers
I have just looked at the brake test and the wagon has passed all tests and it says overall test PASSED so if it did`nt work then it would not of pass or would it
The spring lever moves by hand as this morning it had about 4- 5 ton items i took of my other vehicle for storage the cable the spring connects to was lose, when i unloaded it this afternoon for tommorrow the cable has tighten up.
having an 8 tonne payload you mentioned i assume your brakes are full air?
or is it on hydraulic?
they can pass a brake test if the load sense valve is siezed open as far as the required efforts are concerned,however they will NOT pass as when it is unladen it will still be giving maximum effort to the rear axle brakes causing possible lock up and instability…as for your mechanic missing it…annoying as it is i miss things sometimes(but not often i may add) when i take them for test im only human…the testers themselves miss things too…and of course there aint a driver on the planet who’s never hit his truck ;0)…more info i may be able to help ,however when it comes to brakes dont touch if your sure…
Hello westpark last year summary test results where this
Service 57%, Secondary 26% it says ‘locked’ in brackets at the side, Secondary 31%, Parking 27%
this year results are Service 57%, Secondary 26%, Secondary 30%, Parking 31
now these seem pretty same apart from the last 2 where 1 is lower and 1 is higher then previous year. Last year test weight of vehicle was 15473kg this year test weight is 16269kg i persume this does or will alter the brakes performance anyway.
what make of truck is it/how old?
brake results on rolling roads vary enormously depending on the weather believe it or not…i have put a vehicle on a ministry rolling road for a voluntary and it passed resubmitted it on the same rollers and it failed its test!!!
positioning on the rollers/air pressure how fast you press the pedal will all effect results so dont read too much into comparing last years and current results…
if its a mechanical linkage lay under the vehicle and have someone press the footbrake…if its free and working correctly the lever should “kick” when brake applied…no kick it siezed!!
My truck is a Daf 55 on a R reg 1998 plate, the brake system is on air, i will try and have a look at that again today. let u know later if it is sezied. Tanks for your help and info so far.
fitted the new secondhand value brakes sound different now when putting the brakes on and off. On the link above it says vosa charge a small fee to set up the load sensor value does anybody know how much the small fee is and can i have this done at the same time more or less when i book in for a retest
Cheers for the helpful info and help this is one of the reasons i used this sight as most people do help and it is funny reading some of the post aswell.
clarkie:
Don`t know if this is the right place to post it
What does this sensor do and i notice they is 3 units on the rear of the vehicle near the wheels, i pursume that the value itself is the one where the large spring is on. Does anyone know how it works and verfiy how i can test it before taking it back for the MOT. I would ask my mechanic but they did not spot it when they suppose to check the vehicle over for the MOT.
senses the load you dimwit, what did you think it did
Okey-Didley-Dokely. Look at the title of the post,before you make silly remarks.
A “load senor value” translates the price of Spanish goods. 
Okey-Didley-Dokely. I know what it is and it has something to do with the load on the vehicle but i wanted to know HOW IT WORK. and i take offence to that coment as well. This is 1 reason i don`t use this site all the time cos you get t----rs like you on here calling people who ask reasonable questions.
Vosa will not set your load sense valve mate…what they will do is a voluntary brake test,…these are better cos if it fails you can go away and rectify it and doesnt show up as another fail and it does not refelct on your maintenance or licence if it passes submit it for retset !
there will be a plate on your vehicle somewhere that dictates laden and unladen pressure settings for the valve,you will require gauges and load to do this,if you havent got the kit or the confidence and knowledge take it to your garage mate.