I havent had heat for a long time, everything had been checked, I changed 3 different units, they all have the same problem - will not work, and only a few of the buttons will light up. So, me and a electrician came to the conclusion that it might be faulty signal from the bcm or whatever is called the box next to the ecu in the passenger footrest. Does someone have a service manual for sale? And is there a way I can troubleshoot this module for faults? Had somebody had similar issue, I am out of ideas, this is my daily, if i drive the car on longer distances windows get foggy and you see where am I going. Will really appreciate any help, I am in no way a mechanic, I am still learning, so suggestions are gladly appreciated!
p.s. fuses are good, lighter is connected to the ac with the same fuse, but it works, i've opened the climate control units, they are good inside, nothing burned out, as I said I've checked everything, it doesnt seem to be anything simple. Thank you in advance

 

Look around for service manual downloads.

Is it the same buttons that don't light up on all three HVAC units? If not, it's probably the units themselves, as bulb burnout is common on them.

Also, I believe the HVAC units are year-specific and need to be matched to the part # for your car or all the functions won't work. Are they completely non-functional? I used a spare that did everything except control fan speed, but the indicator bars on the unit itself responded to the button presses.

 

My original one, stopped working, i got one from a junkyard that is non working, and then I used a trusted seller on SC crew for a new one, that has been tested, and still nothing. all of them light up only 2 buttons, not all the same though, I got a service manual, i will start examining it, but i am amazed how no one has that issue....