Citroen XM Forum

The green tinted layer is a form of glue that fixes the foil to the LCD contacts.
On mine here it is restricted to the top edge contact area of the back glass of the LCD.
On these the LCD liquid area looks black without light.
When operating the text goes clear.
When the liquid fails it also goes clear in those areas not cloudy.
The green colour comes from the green plastic sheet behind the LCD.

Just tried a couple of bulb holders fitted with 5050 flat LED's (one white, one green).
They give a fairly even spread of light.
Spread is helped by the LED being multi element and virtually on the face of the pcb, not projecting forward like the bulbs.
At 12 volts they are too bright, the white one particularly so.

John

Just checked the "12v" bench power supply I was using.
It is actually marked as a regulated DC supply 13.8 volt 5 Amp constant, 7 Amp surge.
Might explain some of the LED brightness.
Will see if I can find a 12 volt regulator to stick in circuit.

John

Hi John,

Shouldn't worry about using a 13.8v bench supply for testing and development, especially if it's regulated.
13.8 is not just the normal 12v lead-acid battery charging voltage for basic chargers, but is also the 'preferred' supply voltage for vehicle extras like CB radios and audio equipment.
Most tungsten vehicle/instrumentation bulbs, are actually rated by good manufacturers at 14v, to avoid being over-run by normal vehicle use. Always a good idea to avoid instrument lamps which are stated as "12v".

Just checked on the 2.5, and the vehicle system is running at 14.17v with a fully charged battery and a while after starting.