actually both CA3s are running on the same battery pack. just one CA3 is brighter than the other straight out of the box.
I am not confident opening the CA3s up.
As the posts in izeman's search revealed, the CA brightness is largely a matter of the +5V current drawn by the CA and it's accessories (throttle, etc). So - if you have a three position switch or ebrakes on one CA but not the other, the brightness might be different. Different LED batches might yield slightly different brightness, but I can't speak to that probability.
As pointed out in post (https://endless-sphere.com/forums/viewt ... 8#p1263588
), it's possible to dim the display a bit by bypassing current around the LCD module. Similarly, it's possible to brighten the backlight
by adding a load resistor in parallel with the 5V regulator to draw a bit more current through the LCD module. In that case, you would still need to pay attention to the current limitations determined by the pack voltage as called out in the Guide. For instance, since the CA 5V supply is drawing about 10ma, you might add a load resistor to draw maybe 10-50% more current (1-5ma).
Anyhow, since you don't feel comfortable cracking the case, you can go after this by directly increasing the 5V regulator load with an external resistor. This is probably the 'hackiest' strategy, but will work fine if you need a no-messing-with-CA-internals approach - just pay attention to the overall current inventory as mentioned above. So - you might try jumping a 1K resistor across the +5V and Gnd pins of the AuxPot or Throttle connectors. This would boost the current draw 5V/1K = 5ma which will visibly brighten the backlight
. You could make up a super short M/F JST pass-through extender that has the power leads jumpered with the resistor of choice (use a small 1/8 or 1/10W part - there's no power to speak of). This would let you do the fabrication off the bike on the bench and then just plug in the gizmo when it's ready with no chance of taking your bike out of service with a fabrication accident.