Hey Pals –
I'm entering this post so that anyone searching the forum, or googling this can find the answer, as it haunted me for a couple of months.
Experience / Symptoms:
After doing a full nut & bolt car swap, including replacing my windshield, my F80 heads up display was very dim in the daylight. I was perplexed by this because i had it set at full brightness, and it performed just fine at night.
I was about to mess around with a lot of custom coding, and then i realized that there are coding attributes for HUD light sensor.
At first, i thought that this was the light sensor which is integrated into the driver's instrument cluster - THIS IS NOT THE ONE.
(This specific dimmer only auto changes the brightness of the dash and the iDrive unit, nothing else.
The Solution:
My coder, a guy named Marius (@marius76_bmw on Instagram) scanned my car and noticed that i had the incorrect solar / rain sensor installed in my car.
Long story long, when i swapped all this shit over, i retained the F31 solar / rain sensor in the wagon, instead of swapping over the F8x sensor which is equipped to provide light sensing information to the HUD for auto brightness / dimming.
The correct unit is labeled "4.7" and you can find more information here:
https://www.realoem.com/bmw/enUS/sho...diagId=61_2807
Note - i strongly believe the only people who are likely to experience these symptoms are those who have either retrofitted HUD into their car, and didn't know they needed a more advanced solar sensor, or those who have their unit break or swapped out as a part of a windshield replacement, and have the wrong solar sensor installed.
Certainly not a likely scenario for many, but for the handful of us for whom it might happen, let this post save you time, money, headache, and get back to a brighter HUD faster.
Pics of the full brightness HUD attached:
Cheers buds!