Thank you, very helpful. Didn't have the courage to the disassemble the air slot trim. Blew out the top part with 100 psi. Found a lot of gunk coming out from the fan core. Opened it up blowing 100 psi and repeating the process from top to bottom till the dust cleared out. My fan was just a bit dirtier than pictured. Thirty minutes running with the heater on, no H2 error code. In case the error comes back, I plan spray WD40 and repeat the cleaning process with compressed air. I'm just hoping for the best that it ends here.