Hmmm. 3.3v and not 5.0v? ..
So I'd forgotten that I'd started to trace out the backlight circuit a while ago.. I never completed it (there is a TON of circuitry for something so simple!) but the basics are that the + side of the LCD backlight more or less goes directly to +12v. I forgot that the LCD does not dim with the EL or HVAC backlight, only a tiny bit when the headlights are turned on.
(To be technically correct, it's really car voltage -.8v when headlights are OFF, car voltage -.85v when headlights are on.. (must be through a diode?) So if the car's electrical system is really 13.6v, the backlight power will be 12.75v)
The - side of the backlight goes through essentially 330 ohm + 22 ohm resistors, and a transistor. These are (3) 1,000 ohm 1206 resistors to the lower left of the tachometer needle motor, and a 22 ohm 0805 resistor directly to the lower left of the motor. The transistor is next to the 0805 resistor. It appears that the OEM orange screen had 0 ohm resistors on it, so Lotus (well, the gauge manufacturer) chose to put the LED resistors on their board, maybe so they could change them if needed easier than having the LCD place do it.
The LCD itself has a built-in resistor since it's backlight is intended to run directly on 5v. The red-on-black LCD I have here uses a 330 ohm resistor. So when plugged into the Lotus cluster, it essentially becomes a 682 ohm resistor instead. I'm not sure what resistor the white LCD uses (they're in the mail..) but you can see it on the back side of the screen - should be R8, near where the LED pins are soldered. The red screen I have here is running @ 4.27v at the pins with all the resistors in place, and the LED itself is getting 1.675v. If I short out the 330 ohm resistors on the Lotus board, that only goes up to 1.680v, so not much change.
If your LCD screen has a 330 ohm resistor on the back of it, you can essentially short it out since the Lotus cluster board has 352 ohms already. BUT, all that said, it might not make much difference unless the screen is really drawing some current. (these things use a single LED though, so not likely..) You could potentially replace the red LED for a brighter one (or a bunch of surface mount ones?), but in my case anyway the red backlight in my car is plenty bright at night.. Since it doesn't dim, you don't want it 'too' bright. Just something to think about.
Whew! Lots of info for 6:30am! LOL