DISCO4.COM - View topic - Height sensor question

euangibson

Member Since: 24 Dec 2010
Location: Borders
Posts: 11027

2012 Discovery 4 3.0 SDV6 HSE Auto Firenze Red

Height sensor question

My suspension is playing up (when I ask for access height it goes into extended,believing there is an obstruction under the car apparently)
I am ticking off the possibilites;compressor is seemingly working fine as the car goes up and down freely on all other variables
My question is how do the height sensors work,and can I manually or visually check/clean them myself ? "Better to remain silent and be thought a fool,than to speak out and remove all doubt" ?.....what rubbish...

Locking rear E-diff
RLD spare wheel protector & sump guard
Extended roof rails
Series 111 mudflaps
Black side tubes,grill and vents
Timed climate remote
Hids4u interior lights

D4 Firenze my2012 HSE
D3 Java 2005 SE manual (sold,sadly,thanks for the memories)
1966 '88 Series 2a....still starts in the morning better than I do...

27th Oct 2011 7:21 am

Alex08

Member Since: 09 Nov 2006
Location: Glasgow
Posts: 1600

Scroat under car trying to remove spare wheel?

27th Oct 2011 7:22 am

euangibson

Member Since: 24 Dec 2010
Location: Borders
Posts: 11027

No....the kids are both indoors

"Better to remain silent and be thought a fool,than to speak out and remove all doubt" ?.....what rubbish...

Locking rear E-diff
RLD spare wheel protector & sump guard
Extended roof rails
Series 111 mudflaps
Black side tubes,grill and vents
Timed climate remote
Hids4u interior lights

D4 Firenze my2012 HSE
D3 Java 2005 SE manual (sold,sadly,thanks for the memories)
1966 '88 Series 2a....still starts in the morning better than I do...

27th Oct 2011 7:23 am

BBS SPY
Site Sponsor

Member Since: 15 Jun 2007
Location: Sunny Cyprus
Posts: 3054

2005 Discovery 3 TDV6 Base 7 Seat Auto Bonatti Grey

Quote:
My question is how do the height sensors work

The height sensors are small (50 x 50 x 40 mm approx) sealed blocks with a connector on one face and a rotary shaft type stub sticking out the side face, to which is attached a lever arm at right angles. Moving the arm and thus rotating the stub causes a wiper to move on a track inside the unit (probably made of carbon) and thus causes a proportional change in resistance between the respective pins of the connector. The unit is mounted in such a way that changes in the vehicles height rotate the input shaft.

The EAS ECU applies a very regulated positive voltage to one side of the track and an earth at the other end, the moving wiper then provides a voltage somewhere between the positive feed and ground, depending upon it's position. Although in reality only a small section is used. This voltage is fed back to the EAS ECU which feeds it into an Analogue to Digital convertor (ADC) to get a numerical value for its current position.

It then compares this value against what it has stored as a calibration value for standard height, applying a fixed plus or minus offset for other heights to make a target height (or in reality a target numerical value) and calculates if it needs to add or remove Air from that corner using its valves etc to get the vehicle to raise or lower from it's current height to achieve its target height. Although it does have some tolerance so will accept if it is close.
The EAS system closely monitors the sensor values and expects to see resultant changes from the height sensors according to what it is doing.

The stored calibration value is required because even if a corner of the vehicle is at a fixed MM height, there is some variation of linkages and sensors and even in the mounting holes of the sensors themselves, therefore if you just remove and refit the same sensor the stored calibration value may then be off some.

You can certainly check the linkages and connectors just in case, but the connectors are pretty good and watertight and the linkages pretty well made and not prone to wearing out.

If you have 4x4 info, this just might give you some clue as to which corner the EAS thinks the virtual obstruction is under, but be advised often the problem is with the sensor on the opposite corner.

A Fault code reader capable of accessing the EAS might also give you more info but again faults stored about a particular corner can be due to a problem on another corner.

Of course an MSV-2 would allow you to see and capture the values the EAS sees from the sensors in real time and with playback, and Raw data captures you can retro analyze in Excel, but it's a bit like using a sledge hammer to crack a nut in this case.

Although we do not fix vehicles ourselves i have somehow ended up being involved in a few such mis behaving EAS cases. IMHO if one sensor is already playing up, the rest is not likely to be far behind and replacing them on an older vehicle especially is no bad investment, even if the fault ends up being found elsewhere, which in your case sounds unlikely

Fortunately unlike other LR models like my 03 L322 where one sensor can cost near 100 GBP, the sensors for the D3 are much more reasonably priced and all four will not cost much more. I personally already stock a full set.

They are also not that difficult to fit.

So my advice to you is contact TLO and get yourself a full set.
Fit them and see if the issue is resolved, then, as soon as possible, find someone with equipment to re calibrate your EAS height values.

Please do not postpone getting the re calibration done as a matter of safety.
Imagine that your vehicles EAS height calibration may well be off by 10mm on two opposite corners. This can have a dramatic effect on its equal weight distribution on all four Tyres which in turn can effect high speed braking

27th Oct 2011 4:50 pm

euangibson

Member Since: 24 Dec 2010
Location: Borders
Posts: 11027

Thanks BBS SPY,very informative and helful answer
My car is getting hooked up to Flack's magic box of tricks on Saturday so will see what the outcome is.....sounds like the sensors would be a nice cheap fix compared to some of the other possibilities

"Better to remain silent and be thought a fool,than to speak out and remove all doubt" ?.....what rubbish...

Locking rear E-diff
RLD spare wheel protector & sump guard
Extended roof rails
Series 111 mudflaps
Black side tubes,grill and vents
Timed climate remote
Hids4u interior lights

D4 Firenze my2012 HSE
D3 Java 2005 SE manual (sold,sadly,thanks for the memories)
1966 '88 Series 2a....still starts in the morning better than I do...

27th Oct 2011 6:08 pm

character

Member Since: 31 Dec 2007
Location: wiltshire
Posts: 5781

2005 Discovery 3 TDV6 S Auto Alaska White

would second the view to change ALL sensors at the same time and recalibrate the suspension AND steering sensor - word of caution however, you might well find that in its past yer d3 might have had the nsr or osr changed, this could mean the wires will need to be spliced in further down the loom, might want to get yer friendly LR stealer to do the job or send a mail to TFC to see if its his bag

27th Oct 2011 11:14 pm