Member Since: 13 Mar 2007
Location: Dorset
Posts: 236
SATNAV dimming
hi all,
on two mornings so far this week i have got in the car started the car (after waiting for the glow plugs) , accepted the L/R warning on the sat nav and as i put the screen heater on the sat nav dims like when you put the lights on..
switch of the screen heater until a mile down the road then back on no dimming in the sat nav..
any ideas?four wheels - Buckingham Blue SE, tints, PTI, (SOLD)
About to sell up and take a Gap year following a VERY full 23yrs 9 months and 24 days (not that im counting)
31st Dec 2009 11:13 am
J@mes
Member Since: 10 Nov 2008
Location: Bomber County
Posts: 4547
how's your battery?
could the heated screen be causing a volt drop leading to the screen dimming?
whats it like if you switch all the heated seats on?2014 D4 XS
2005 D3 SE - Gone
31st Dec 2009 11:16 am
smac343
Member Since: 13 Mar 2007
Location: Dorset
Posts: 236
that was my first thoughts James i will have a try on the next cold morning and see if it gets worse with a bigger load.four wheels - Buckingham Blue SE, tints, PTI, (SOLD)
About to sell up and take a Gap year following a VERY full 23yrs 9 months and 24 days (not that im counting)
31st Dec 2009 12:27 pm
crwoody
Member Since: 09 Mar 2009
Location: Littleborough
Posts: 2109
I noticed a similar thing with mine the other day. Early start - very cold - nav screen very dim, worse on left side but flickering too? so dim I could barely read it. I stopped after half a mile or so, turned everthing off and re-started - now OK, very odd
Did the same a couple of days later, also very cold.
I dont know if its the same fault as yours smac, but I didn't notice any connection with the screen heater on mine though. it appeared to me like a temperature issue, LCD's don't like big variations im temperature, (generally.)
I checked the battery on mine 2 or 3 days ago after the car had been standing all night at about -3° or less and it showed 12.1 volts with the car "semi woken-up" ie. interior light and display screen on (to open the bonnet) then 14.15 volts with the engine ticking over.
Might be worth checking your battery after its been standing for a bit if you have access to a meter.Clive
31st Dec 2009 1:02 pm
MARKW
Member Since: 29 Aug 2008
Location: SW
Posts: 2390
I've had this the last couple of days but very slightly different. Whilst driving along with the front lights on with no other major drain on the batt, the screen would dim down then flick back to full brightness, then about 5 mins later would do the same thing. This went of for the 1 1/2 hr drive home. Will get them to look at it when it goes in for it's recall work.HONI SOIT QUI MAL Y PENSE
They shall not grow old as those of us left grow old. Age shall not weary them, nor the years condem. At the going down of the sun, and in the morning WE WILL REMEMBER THEM
31st Dec 2009 1:56 pm
hensoni
Member Since: 01 Oct 2007
Location: Sleepy Somerset
Posts: 576
Don't forget that your LCD screen needs to warm up too. The backlight for the LCD is a Cold Cathode Tube - effectively, a fluorescent tube. This will most likely have a heater element spiraled around it to get the tube to an optimum temperature (quite hot, 50 to deg 60C). When an LCD itself is cold, it is very slow to respond, couple this to a Cold Cathode Tube that is working hard to push lumen through the already in-efficient display and you could end up with a dim, flickering display.
If you use energy saving bulbs in your unheated shed, you get the same effect - c0ck all light until the electrons get warm and excited. Self warming of the electronics will only take a few minutes from the sort of cold soak temps that we get in the UK but those in Canada, Sweden, Alps, etc will notice a much more dramatic effect as they are cold soaking at minus 20C or worse. LCD screens for aircraft are often qualified for operations down to minus 40C but they can take 20 minutes before they are warm enough to display anything useful.
Dodgy battery connections and a plethora of electrical loads can only make the situation worse. I've never come across a car that does load shedding or staggered switch on (like wot an aircraft does), the poor old battery has to take the lot.
4th Jan 2010 12:57 pm
robertm
Member Since: 23 Oct 2008
Location: holmfirth
Posts: 14
the screen is fine its because the car is using power for other things i phoned land rover with this its fine, doesnt look right i must say.
Might not look right, but you leave any screen in the car in temps of -5 to -10 and you'll get a similar performance from it for the first couple of minutes. I understand the D3 does hold back on providing full power to some systems until vehicle startup is complete and the battery is recharging, but cold weather impacts on a) battery performance and b) power requirements so something will always have to give. The screen is a more noticable aspect of "give", but not one that prevents you moving, which is the primary purpose of the car.
I know it's not considered "kind" to say no these days, but no. Just no, ok? And if it's not ok, still no.
7th Jan 2010 4:00 pm
boyter
Member Since: 13 Jul 2009
Location: Dubai
Posts: 14
I've seen this happen from time to time on My D3 too, usually on long journeys. Its totally sporadic and I've never had lights on at the time i've noticed it.
It still works, just very dim and hard to read in sunlight.
I live in Dubai so it takes the cold weather out of the equation!LR's and racing...
Member Since: 11 Sep 2006
Location: Swine Town
Posts: 2330
Fairly common for cold cathode lighting in the cold I believe (not sure why it would happen in Dubai tho!).
Until the tube gets some heat in it the tube-driver seems to struggle in continuing ionisation. This may be because the tube relies on the heat generated by the lamp whilst it's active to produce more electrons to continue the 'strike' across the tube. Mny tubes are of this kind. Until it's warmed itself up, the driver circuits may note the current dropping too low and send another high voltage spike to re-start the ionisation. This is probably why the screen flickers.
As far as I know, there is no problem with this other than it can be annoying/distracting, but the extra cost of a tube with a beta radiation source probably wasn't worth the H&S paperwork to implement.Dr. Ian Malcolm:
"Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should."
Transgenic tomato anyone?
Mine randomly goes dim, just though it was me.
"I know that you believe that you understood what you think I said, but I am not sure you realize that what you read is not what I meant"
12th Jan 2010 2:17 pm
hensoni
Member Since: 01 Oct 2007
Location: Sleepy Somerset
Posts: 576
The number of reasons could be wide and varied and subject to considerable speculation. However, looking at the wiring diagrams for the infotainment system (thanks to this forum ), I would suspect that the problem is simply due to voltage drop.
The positive feed is fed from a 0.75mm cable, spliced down from a 1.5mm cable which is terminated to the fuse. Other users are the satnav dvd player and the head unit.
The return feed however is a pair of 0.5mm cables, spliced into a 0.5mm cable, which is then spliced with other return paths into a 2.5mm cable, which then is terminated at the body.
Voltage drop along a length of wire is current dependent, the higher the current drawn, the greater the voltage drop. LR have spliced the return path (a pair of 0.5s) into a single 0.5 cable and this is likely to be the pinch point. If the positive feed needs 0.75mm, then so does the return (unless it is a considerably shorter run).
0.75mm cable has 1.5 times the cross sectional area of 0.5mm cable with a corresponding reduction in impedance / metre of run. The only way to investigate any further would be to run a nice fat cable from SJ590 to the battery -ve terminal and see if the problem disappears. I would guess that the splices are sealed so any interference is more likely to cause more problems than it solves.
We also need to assume that LR and their suppliers have designed the power stages of the components correctly and we aren't suffering (for example) from conducted emissions in a DC-DC power supply in the nav unit interfering with the display...
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on the sat nav and as i put the screen heater on the sat nav dims like when you put the lights on..
), I would suspect that the problem is simply due to voltage drop.
