At least on my Predator, the factory part cooling blowers are 24 volt, 0.2 amp Boosfan JD4010M, and they truly suck. They barely move air.
I replaced them with Delta BFB0412HHA-A units, wired in series to just one FAN0 connector. These are 12 volt, 0.08 amp units, and are physically a drop in replacement. I use two in series electrically so that each drops 12 volts, and the pair can run off of the same 24 volt FAN0 connector with the same PWM.
Although it is not considered "best practice" to wire BLDC motors in series, these are locked rotor protected, so that unless one blower fails shorted phase to phase (very unlikely), their low current draw and high impedance will prevent catastrophic results.
Why do this? The original units would barely start at 75% PWM, and barely move air at 100%. The new units actually start moving at about 5%, run smoothly and reliably at 10%, and will lift the printer off the bench at 100%. Just kidding, but the airflow is astounding, and actually having real air speed control over a large range is a huge benefit. And no monkeying with PWM settings in Marlin, either.
Plus, the new Delta blowers have dual ball bearings, so they should last for years. I don't know what the old blowers had for bearings, nor do I care, since they barely worked anyway. I may dissect one to find out.
The Delta blowers are commonly available from many sources, starting at about $7 each. I got mine in 2 days from Mouser for $14 each.
I use the Bakak duct from Thingiverse, and highly recommend it. The factory original duct basically just blew on the nozzle with the anemic air flow from the factory blowers, and I got rid of it long ago.
EDIT: I opened one of the old Boosfan JD4010M. It doesn't really have ANY bearings, per se. Just a plastic shaft rotating directly in a hole in the plastic housing. It's a miracle that these things spin at all.
Edited 1 time(s). Last edit at 02/08/2022 07:10PM by rq3.