air won't turn off on 2004 Nissan Quest

my air conditioner doesn't turn off it's always running,all dials are off

Asked by for the 2004 Nissan Quest
I've been told that this is possibly your problem.

Customer Concern: HVAC. Has the auto a/c system. The fan is running on high speed at all times. You can turn the control panel completely off and the blower fan is still running on high speed.
Tests/Procedures: 1. Check for a voltage signal on the Blue/Yellow wire at the fan control amp . If it has a no voltage, then the fan amp would be bad. If it has a continuous "high" voltage signal, then the control panel may be at fault. For low to medium speed, it should have 2 to 4 volt signal, for high speed, it should be about 9 to 10 volts.
Potential Causes: Blower Fan Amplifier

1 more answer
It's possible you have a broke A/C fan switch