X1 Carbon 3rd Gen - Trying to get working

[amujee]

I bought a "parts only" X1 Carbon 3rd Gen and I'm trying to get it to work.
When I press the power button, the fan spins up then stops, keyboard lights up and turns off, and power button light remains on.
Nothing on screen, no post, and no beeps. Same behavior on either I plugged in an external monitor but there's no signal. I assumed motherboard is bad and needs to be replaced.

Bought a used motherboard that was supposedly pulled from working laptop with smashed screen. Installed it and plugged everything in except battery.
As soon as AC power is plugged in, the power button light blinks 3 times. Nothing else happens. If I press the power button, it blinks 3 times and then nothing.
I plugged in the battery and same thing happens when I plug the power in, but power button won't respond any more.

Any ideas? I'm not sure if I should try a third motherboard or cut my losses and sell everything off for parts.

*Ended up getting another motherboard. Hoping this will be it.

[jdhurst]

It sounds like the second motherboard was also bad. Let's hope the 3rd one is good.

I have an X1 4th generation. Everything including CPU and memory is soldered to the board so let's hope this is it