Try reseating the connectors from the power supply and printer control board, and do a trouble reset... if that doesnt fix it, youre in for a whopper of a bill for a tech to fix it.
Solution ID
TAUS0702826EN* Solution Usage 2
Description
C-3823 and/or C-3923 are indicated. The connections for the fusing unit, from the power supplies and the printer control board, have been re-seated.
Solution
CAUSE: Faild IH power supply (IHPU).
SOLUTION: Replace the IHPU (p/n A00J M400 03).