P38 HEVAC and Message Center Display & Control
Panel Backlight Repair
& Control Panel Backlighting
Replacing the Hevac Control Knob Illumination Bulb
A number of owners have noticed the dimming of some of the LCD information displays used in their 4.0/4.6 Range Rovers. It is important not to panic when this happens; it does not necessarily mean the climate control system or the message center or even the BeCM has failed! Much more likely, it is simply a matter of light bulbs that need replacing.
The various LCD display panels are lit from behind by simple incandescent bulbs. Ron Beckett of Australia has been kind enough to supply the following details on how to replace them, and the technique and photos for replacing the bulb behind the control knob (above right) were supplied by Joseph Romanello. Some owners in the US have had trouble finding the bulbs at sources other than the dealer, so Ron has supplied details where possible for low cost generic parts.
HEVAC Control Panel Backlighting
Accessing the Rear of the Panel:
If you are only replacing the bulb that illuminates the control knob, you can skip ahead to that section below. However if the LCD display or the vent controls are not illuminating (including the blue/red arrows for the passenger side temperature selector, and the A/C off and recirculate buttons), the first order of business is to gain access to the rear of the Heating, Ventilation and Air Conditioning (HEVAC) control panel. This is a complete unit containing the ECU for the heating and air conditioning, the control switches, and the LCD information display. The display backlight bulbs are mounted in the rear of this panel, two at the top and two at the bottom. Because of the way the dash is fitted together, removing the control panel requires removing the trim panels on either side of the center console. This is a slightly tedious procedure but is covered in illustrated detail on our Center Console Side Panel Removal Page. When you have removed the side panels, the four screws holding the HEVAC control panel in place (photo below left) can be removed and the panel can be pulled rearwards (restrained by the wiring harness). I found it desirable to remove the two left hand multiplugs on the panel in order to pull it out enough to access the bulbs.
The right hand pair of screws
holding the HEVAC control unit in place
HEVAC Control Unit Reference Diagram
There are 5 globes for back illumination of the HEVAC control unit. Four of these globes are in Osram holders and are accessible from the rear of the HEVAC panel. Two globes are are at the top of the panel and two are underneath. The HEVAC panel illustration in the parts catalogue only shows the top two globes. (See the HEVAC panel diagram above to reference the bulb numbers used below).
To show more clearly the positions of four of the bulbs, Ron took
the above picture with the front panel of the control unit removed.
The next picture (below) is of the back of the circuit board inside the
control unit. You can see the plastic
cover over the LCD which is illuminated by the 2 watt central bulb (#3
in the ensuing description). To replace the bulbs, you do not have to
dismantle the unit this far; these photos were kindly supplied by Ron
to better illustrate the purposes and positions of the various bulbs.
When you remove the HEVAC control unit, the rear of it will look
like the photos below. In these photos, Ron took
globes out so that you can see where they fitted - they are the small
circular sections that can be seen from above and below.
above the white rectangular section on the HEVAC Panel Top, is the rear
of the holder for bulb #7 in the parts catalogue drawing - barely
because it is black.
Top Rear of HEVAC Control Panel showing sockets for bulb numbers 3 and 4. Bulb 3, in the center, illuminates the LCD panel.
Underside of Rear of HEVAC Control Panel showing positions of the other two bulbs
Bulb #3 in the HEVAC panel reference drawing is a 2w globe and it illuminates
the LCD screen. The actual globe is the same as the globe #7 but is
welded to the holder contacts. Ron thinks it could probably be replaced
without buying a new holder but it would probably not be worth it. (See pictures below)
LCD Backlight Bulb & Holder
The other 3 globes in holders are 1.2 watt. These lamps are in black
holders (LR Part No.STC3868). The lamp voltage and wattage rating
is moulded into the lamp holder. These items are listed at A$3
(US$1.50) by the dealer network in Australia. These holders are
to the holders in my daughter's Peugeot 405 so that may be an
source. You can see you are not locked into Land Rover for these
Note: Before going out and buying new bulbs, make sure the old ones are actually burnt out! Joseph Romanello found that his were just rotated so the electrodes weren't contacting each other. A simple twist saved a lot of expense because his Land Rover dealer wanted $5.18 per bulb!
Replacing the Control Knob Illumination
Bulb (# 7)
The fifth globe (#7 in the HEVAC panel diagram) is a standard 12 volt 1.2w wedge base globe (see illustration below under "Message Center and Odometer Display Backlighting") as used in the Classic and the Mk II instrument panel. Joseph Romanello figured out how to remove the fan/auto switch off the HEVAC panel to allow access to this globe, which is not removable from the rear. Joseph reports that you should grasp the entire circular knob with the thumb and first three fingers (see photo at top of this page). Squeeze gently inwardly and pull STRAIGHT out. The knob must be pulled straight out because there are two long plastic rods which anchor the knob into the console and you could sheer one or both off if not pulling straight out. (I found out the hard way and had to superglue one back on before I could replace the knob). Ron Beckett notes that "The parts catalogue says "Knob, heater/fan control. NLA Supplier advises not possible to service the knob without endangering the integrity of the control panel." (Section L, page 14)." So exercise caution here!!
Bob of Leicestershire, England, used this method to remove knob & replace the bulb. He adds the following tips: "I found that one of my prongs on the push part of switch was shorter than the other, but still located in its slot. It's only used for location, and is not used to hold the knob in position. What holds the knob in place are two blades that stick up from the clear plastic part of the switch, mounted, onto the front panel; this rotates for selection of fan speed. On these blades are molded small wedges that mate onto the inside of the revolving part of the fan switch. One is larger than the other so it will only fit on one way. The easy way to replace the switch is to mark the top of these blades with a marker pen and and put two small scratches onto the actual outside of the revolving part of the switch in the centre of the blade slots, then place prongs into their slots and rotate the fan part of the switch till scratch marks line up with the blades and then push on. You will also find that the next time you need to replace a bulb, all you need to do is pinch the switch at 90 degrees to your scratch marks, and it will pop off.
Ron partially dismantled his control panel and took the photo below to illustrate that the bulb that illuminates the knob also supplies the backlighting for the far right hand button (on the left in the picture). One can make out the pieces of clear plastic that take the light to the buttons. That is why if the knob light fails, all the illumination fails on the RHS of the unit.
below (supplied by Joseph) show
what the unit looks like with the knob off (one close up, one farther
away). Simply grasp the bulb and pull it out and replace (photos
Control knob removed
Control knob mounting showing
Message Center and Odometer Display Backlighting
Symptoms and Repair Procedure
Kevin Kelly noticed one weekend that half the backlighting on his 1998 Range Rover's dash where the mileage and other information is displayed stopped working. He could still see the numbers, but just barely. Ron Beckett reports he recently had a similar problem and had solved it by replacing the bulbs that supply the backlighting for the display. Ron tells us this is an an easy job; the display is LCD and is illuminated from the rear by 1.2 watt wedge base globes (bulbs). They cost about A$1 each (US 60 cents). The globes are in twist lock holders and can be a little hard to pull out of the holder but they will come out (grip the glass bulb in your teeth and pull - oh, don't bite too hard!).
Wedge-base Bulb for
To replace the globes requires removal of the instrument binnacle. This is an easy enough job but a little long winded. Our Instrument Binnacle Removal page covers this operation and includes some suggestions not mentioned by the manual.
Note on Sources and Part Numbers for this bulb:
Kevin had some difficulty finding generic US sources for this particular wedge base bulb. Ron Beckett noted that there is no problem sourcing them in Australia or the UK, and noticed that his daughter's Peugeot 405 uses the same globes (he had to replace some). For a picture of the bulb -- see the illustration above.
Ron kindly did a web search for this bulb and offers the following information. He suggests browsing to Don's Bulbs for more details. The replacement bulb is the "286" types, with the following specification:
Amp/watt: .09A / 1.22W
Lumens: MSCP:.57 (candle power)
Notes: Indicator and Panel
Equivalent Part Numbers:
If you have corrections, comments or suggestions, email us.
Page revised February 2, 2012