Hello I received a new x1c, after unpacking, after starting to print several benches, the extruder motor broke down. support center sent a new one. I got it today and changed according to all the instructions. (as a completely new user) it was a bit of a challenge. but now other problems appeared, the hotend does not work anymore, the extruder motor does not work.
I tried disconnecting and reconnecting all the cables four times. but nothing helped., the extruder doesn’t work, the heatend doesn’t heat up either. please help me to solve this problem so that I can finally start using the printer.
By the way, the lighting and fan on the front cover also do not work 
I am afraid you’ll need to rely on support for this one. It is clearly much more than the extruder motor.
And with something like the TH board, you will not be able to activate a new one without Bambu support.
If it is still in warranty (the date of reference is the day you filed the original ticket), it’ll probably be much easier to request a replacement unit rather than running the replacement gauntlet.
Good 
and keep your spirits up. Support can be slow, but they try to help as best as they can.
bought a month ago, received a couple of weeks ago. yes, it is guaranteed. brand new
Then it is best to update the ticket with the error messages, a new log, plenty of photos and mention that since it is still in warranty, you’d want a replacement rather than further tinkering. You’ll need the box it came in, patience and resilience, but you should be able to resolve this with Bambu.
If you do not have the box anymore, Bambu also offers another way. It requires you to place a deposit up front though. I had to take that route last year and had a good experience with it. The time to get to the replacement printer was quite stressful though.
Good