Corsa Display only at night

Got a P reg Corsa with a problem with the clock/temp display
backlight.

The Display will only light up when sidelights/headlights are ON so
during daytime the display is dead. Any ideas or wire colours to
check?

Note. The car came with a Kenwood radio fitted, I have cut the Red
with Grey tracer wire on the display to stop the display going dead
when radio is on but this does not affect the problem above eg
reconnecting it makes no difference. The car came with the display
problem.

Thanks in Advance

 

I imagine it is because you have a non standard stereo fitted but are
you sure the dash lights have not been turned down dim?

Alan

 

Hi Alan I also thought it was caused by the non standard stereo but it
was an actual fault in the display, I have posted below 2 other posts
that I posted on another group. Maybe usefull for others on here with
this type of display.

Regards


<First Post>

I checked the black wire from the ignition switch all the way to the
actual track on the PCB and get the 12v OK, can we be sure this is for
illumination?

I also checked the Grey with Black tracer wire which is from the spedo
illumination (via the dimmer potentiometer) This goes through a large
surface mount resistor then a large wirewound 10 ohm resistor then
onto the bulbs. this works fine.

Also on the clock PCB is a small 2A PNP transistor (FZT 753) the
collector of this is connected to the bulbs, the emitter is connected
to the clock red wire which is a permenent 12V feed (even with
ignition off, this 12V reads OK on the emitter).
So I am assuming that when the ignition is on (Black wire live)
there should be a signal to the base of the transistor to illuminate
the clock during daytime. Then when side lights are ON the transistor
switched OFF to allow the potentiometer (dimmer) to control the
illumination.


<Next Post>

I unsoldered the 2A transistor (FZT 753) and checked it with a meter,
it was totally open circuit from Emitter to Base. A new transistor
from a local electronics shop was 85 pence. Fitted this and now works
great.
Answering my own last question, when the ignition is on the clock is
at full brightness, when sidelights are switched on the brightness
roughly half's (with dimmer on full).

So the clock lights rely on this transistor for daytime illumination
(approx 1.8V on the base of the transistor) switched by the black
ignition wire signal (but actual votlage to the bulbs supplied by the
red wire via the transistor). Then when sidelights are ON the
transistor is switched off and the bulbs powered by the Gray with
Black tracer wire (normal spedo lights via potentiometer)

Only other thing to add that caused confusion is when the clock has
been totally disconnected in this way, upon re-connection it will
PERMANTLY illuminate (ie even with ignition off) until the clock time
has been reset, then will function correctly off the ignition key.