I just had that happen myself, well not seize totally but it made an awful squawking sound when it started up. You can take the plastic cover off and put a bit of
3 in one oil on the fan blade shaft, then turn the fan until it moves smoothly. You may need to disconnect your chiller from your system completely and tip it on its side slightly (don't forget its still full of water...I did
) to get the oil to move into the motor part if thats where its seized. I ended up taking the entire fan mechanism out to deal with it. Its attached by two bolts (you'll need a torx screwdriver set and a crescent wrench) underneath and it comes right out except for a few wires and stuff. My chiller had a lot of dust inside so maybe go at it with a vacuum while you're at it.