no heat

Hello! I have a 2014 Armada. Yesterday when I turned on the heat, only cold air came out. I checked the coolant level and it is fine. There was also a strange humming sound that lasted about 10 seconds after turning the car off. Any thoughts on what the noise could be? Are the 2 related?

2014 Nissan Armada SL About two months ago my heater stopped working. So I started looking around for solutions. Long story short I replaced the heater control Valve and the blower resistor on the passenger side of the truck. Yes, the heaters working again. The only problem was, the AC would...