Sub-Zero 550 Fan Vibration. Our 15 year old Sub-Zero 550L has developed what sounds like a noisy

Question

Our 15 year old Sub-Zero 550L has developed what sounds like a noisy fan. We have a loud vibration that comes from the upper portion of the unit. The noise stops as soon as the refrig door is opened and starts up when the door is closed. Noise greatly diminished after we vacuumed upper cooling fins, but returned the next day. Do we need a new fan, or just better cleaning? Does the whole unit need to come out to access the fan?
Thanks for any advice.
Len