The ones that are not in use still do not illuminate when they are in use. It won't be that expensive to change the bulbs. I just ordered them for 1.47 USD each from my local infiniti dealer. 4 bulbs = 5.88 USD.
I have taken the a.c. contol off before to install an aftermarket stereo.
It isn't that hard and not that expensive. And again. When the a.c./heater is in use, the non-illuminated buttons don't light up.
Here is the article:
http://www.fuzzycats.com/docs/ac_controls_bulbs.pdf
Check it out.
Thanks,
Geoff.
P.s.
If it works, I will post a reply to let you know.