The unit will blow cold air when it has reach the humidity level you've preset it on. Once the humidity level rises again, it will start blowing warm air again to adsorb water. Hence, when it is blowing cold air, its in a "sleep mode" till the humidity rises again.
We recommend to purchase a hygrometer to monitor the humidity at your home and compare it to the machine's function. For example, if your unit is at 60% but its blowing cold air when the humidistat shows 75%, then we can further investigate if there is an issue with your unit.