Try these 3 things in order of likely cause:

1) Make sure F7 fuse is good. Pull it and look for a hairline crack in the element. If the fuse contacts in the fuse box are tarnished use a dab of metal polish on a q-tip and clean them. No abrasives! Also make sure it's a copper and ceramic fuse.

2) Look near the brake booster, there should be a green vacuum hose coming from the cabin into the engine compartment. Follow that hose, it should end up on the vacuum splitter atop the vacuum pump. Make sure the hose is not split or cracked. New hose available from Pelican.

3) Start the car and cut or tear a 1" square of paper. Put it on the grill opening on the upper control panel adjacent to the dome light. The paper should suck to the grill and stay in place. If not the aspirator fan is bad, this draws ambient air over the cabin air temp sensor. This is the feedback for regulation of the temperature.

I saw you replaced the aspirator fan but let's do that check anyway to make sure it is drawing good across the sensor.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech