2007 Nissan Titan heater trouble

Maintenance/Repairs
,
1

Heater doesn’t work. I replaced the heater water control valve under the hood on the firewall. When I turn the temp. control knob to the right I hear a buzzing noise that runs for about 15 seconds. When I turn the key off I hear the same buzzing sound if the knob is turned to heat. If the knob is turned to cold I don’t hear the buzzing when I turn off the key. The AC cold seems to works fine.

2

Probably the blend door. The buzzing noise is probably the actuator.