[Stewart]

I meant to ask this while ago, but can cause the light's on the computer display on an auto to go dim then bright again.
It doesn't do it all the time but aften enough.

 

[djtaylor]

Biggest culprit is probably you.

Moving your hand over the sensor is a great one for starters, being either light or dark outside is another.

Try putting your thumb over the photocell on the trip computer and you should find that because it thinks it's dark, the computer display dims.

David.

 

[Stewart]

What!, no just happens when I driving, or if I stop (as in stopped and going away for a while) and start again.
I dont "wave" in front of anything (I dont think) when I'm driving.

 

[djtaylor]

Maybe it's a bit too oversensitive to ambient light? Sun out/clouds and so on?

 

[Stewart]

If thats that case, how can/would it be adjusted.

 

[robjgc1969]

This happened on my car just as you describe for amount 3 months then then the display went dim. It was the light sensor in the trip computer that was dying.

 

[djtaylor]

I wouldn't expect it to be adjustable. It's a photocell, nothing more. It changes resistance based upon the light hitting it, if it's faulty, it gets changed.

If you want, remove the unit and I'll change it for you.

David.

 

[robjgc1969]

The photo cell is not adjustable. However when it is on its way out it can work correctly or go open circuit. If its on open circuit the panel will go to maximum brightness. If you go over a bump or hit the clock you will jar it back to working and it will go from maximum brightness back to the normal setting. This wont last long before it packs up completely.

 

[djtaylor]

Incidentally Axl, the bit being discussed here is the component with the red window at the top right of the picture on the PCB here

 

[Stewart]

Sorry thats not it, I meant the display thats sits under the speedo.
Y'know it has D,R,1,2,3 and the engine check ect.

 

[wrighar]

Originally posted by Axl:
[qb]Sorry thats not it, I meant the display thats sits under the speedo.
Y'know it has D,R,1,2,3 and the engine check ect. [/qb][/b]

That red dot on the SCC controls the brightness of both the SCC and the one under the speedo

Andrew

 

[Stewart]

Sorry, I didnt realise.

 

[Skiddins]

Is the bit under the red plastic lens replaceable, if so, what is it's component value or part number?

Thanks
Skiddins

 

[djtaylor]

Any electronic component is replaceable

Looking at it, i'm of the opinion that it's a phototransistor but still could be a photodiode. Unlikely to be an LDR.

The only tricky bit is identifying it and the pics of mine don't show enough detail. Trouble is there are literally so many of these things to choose from. I would be surprised if this part failed regularly though.

David.

 

[Skiddins]

Could this component be the cause if the brightness of the ACC system seems to be fine and not vary at all.

I have also noticed that sometimes after I have been in the car on a longer journey or in hot weather the display will suddenly become brighter.

Would replacing the unit pictured solve all this, or is everything linked to something else?

Out of interest, whats the large grey 'bubble' in the center of the PCB?

Thanks
Skiddins

 

[mark e]

It's just the lower portion of the dash display, and possibly the DCC that are affected by the LDR. The ACC panel is linked to the rest of the panel illumination that is governed by the dimmer to the right of the steering wheel.

The grey bubble is the lamp that illuminates the DCC.