When i first turn on my range hood the motor spins slowly and then after about 2 min it will finely get up to full speed. It seems to be getting worse over time. Its a new unit never installed but i bought used so im assuming warranty does not even apply.
I'm assuming that the unit wasn't used for a while (years?). If so, the lubricant in the motor is probably viscous (old and thick) and as it heats up it becomes less viscous allowing the motor to spin more freely. The lubricant may also not be lubing as well as when it was new - or has migrated to places it doesn't do any good, hence it's getting worse. Please advise make, model, year of manufacture, etc. You may need a new motor, or perhaps the fan impeller is the issue - same story about the lubricant if it's the impeller (bearings) that are the source of the problem.