2007 Nissan Titan heater trouble

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.

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

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