Every attraction needs to be fixed and cleaned up from time to time. Yes, even inside Disneyland! The Haunted Mansion, which just celebrated its 50th anniversary, will close down for a short period of time as it undergoes renovations! But no worries... it's not as drastic as people think...
According to ComicBook.com
The ride itself, as well as the design of the attraction will be staying the same. There is simply a lot of upkeep to do on both the interior and exterior of the mansion, and it'll take a couple of months to get it all done.
The Orange County Register reports that the renovations and refurbishments are slated to begin on January 21, 2020, and will last approximately two months. The Haunted Mansion should reopen in late March or April.