Problem fan after a short Small Cooling Fan

For the "Small Cooling Fan", because they can all work within 12 ~ 30V, 12V considering the wind speed is too low, 30V high fever, do not take 18V big problem, but we have to test the lower and upper and lower limits to measure its ability to start The upper limit of measuring its heat and heat resistance, because the bad environment, the temperature is very high "Small Cooling Fan" to work, if the work can be stable at high voltage, the thermal stability is better. However, "Small Cooling Fan" long run, over a two to three years will generally bad, we must consider the insurance, especially its power supply in parallel with the relay coil, we must consider a good fan after a short circuit.