220V Cooling Fan drive failure how to do?

Low-power "220V Cooling Fan" drive, which has a number Senlan inverter fan, and some fans are quoted directly from the input AC power supply, in part fan is to take power via the DC bus voltage, and then to become 24V-- a fan control panel - and then provide power to the fan; and the need to distinguish, and one by one investigation; the SEW small power inverter fan does not turn does not mean "220V Cooling Fan" really fails, the fan is subject to cabinet the temperature control, the temperature did not reach the set value, the temperature switch does not operate, the fan will not start, do not move at this time does not mean that a fan failure; so according to the situation, analyze "220V Cooling Fan" control loop, then one by one investigation.