How to replace heater selector switch - 2004 Nissan Sentra

It could be something as simple as a blown fuse or the blower speed switch is bad.

I would first check the fuse for power with the key on. Check both sides to make sure it's at least receiving power. You can use a cheap tester that lights up for the check.

IF the fuse checks OK then it's time to check the blower switch or make sure the heater selector isn't in the "OFF" position.

On some GM vehicle the heater control selector that lets you adjust from floor, to defrost, to dash vents, etc. has an "OFF" position when the selector is adjusted to the far left.

Without physically being there to actually look at it, these are the only suggestions I can come up with.

Hope this helps.

Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob , mounted on the heater function selector switch, which is part of the heater control .
• The function selector knob has the following positions: OFF, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST.
• The heater function selector switch combines a vacuum selector valve with an internal electrical switch.

• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318) . Refer to the System Airflow Schematic and Vacuum Control Charts.
• An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the heater blower motor switch (18578) .
• The position of the function selector knob determines the manner in which the system will operate.
• Each position of the function selector knob is detented for positive engagement.
• You probably have a vacuum leak , Pull heater control panel an check for vacuum . A broke vacuum hose or The vacuum selector valve is bad ! Or check for a vacuum hose in the engine compartment being off somewhere !
  

. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ?
Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
• The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
• Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch (18578).
• The position of the function selector knob determines the manner in which the system will operate.
• Each position of the function selector knob is detented for positive engagement.
• Vacuum Control Motors The vacuum control motors (18A318):
  
  • are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
  • direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
  • The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).
  
  

Most of the time when a heater blower quits working it is the blower switch that fails rather than the motor. Blower switch can be accessed in the dash panel.

I would follow the 5/8 inch heater hose to the firewall and look at the heat control valve position when the selector on the dash is toward cold. Then I would move the selector switch to hot and look at the valve position again. If it has not changed the cable is not operatiing the switch and needs replacing (providing the sdash selector is operating.

it's either the blower motor switch or blower motor resister. Resistor ?Heater Blower Motor Switch Removal Remove the battery (10655) ; refer to Section 414-01 . Remove the battery tray. Remove the screws. Remove the battery tray. Disconnect the heater blower motor switch resistor connector. Remove the heater blower motor switch resistor (18591). Remove the two screws. Remove the heater blower motor switch resistor. ----------------------------------- Switches Removal Disconnect the battery ground cable. Remove the center trim panel; refer to Section 501-12 . Remove the control assembly. Remove the screws. Remove the control assembly. Remove the A/C-heater function selector switch knob. Disconnect the vacuum harness connector. Disconnect the A/C-heater function selector switch connector. Remove the A/C-heater function selector switch. Remove the screw. Remove the A/C-heater function selector switch. Remove the temperature control switch knob. Disconnect the temperature control switch connector. Remove the temperature control switch. Remove the screw. Remove the temperature control switch. Remove the heater blower motor switch knob. Disconnect the heater blower motor switch connector. Remove the heater blower motor switch (18578). Remove the screw. Remove the heater blower motor switch. ----------------------------

First, feel the heater hoses going into the firewall under the hood. If they are hot, then you have hot engine coolant going into the heater core. If they are not hot, then you either have a bad thermostat or you are very low on engine coolant.

Next you need air flowing through the heater core so it can come out heated through your vents. If the iar is flowing somewhere else, your temp blend door is not moving because the bend door motor is bad or your temp knob on your heater controls is bad. The blend door motor is an electric motor.

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Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob , mounted on the heater function selector switch, which is part of the heater control .
• The function selector knob has the following positions: OFF, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST.
• The heater function selector switch combines a vacuum selector valve with an internal electrical switch.

• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318) . Refer to the System Airflow Schematic and Vacuum Control Charts.
• An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the heater blower motor switch (18578) .
• The position of the function selector knob determines the manner in which the system will operate.
• Each position of the function selector knob is detented for positive engagement.

Temperature Control
The temperature control operates in the following manner:

• Temperature control of the heater system is determined by the position of the temperature control knob (between COOL-BLUE and WARM-RED) of the heater control .
• This control knob is connected to a potentiometer mounted in the heater control . This potentiometer is electrically connected to the electric blend door actuator that operates the A/C air temperature control door.

• Movement of the control knob from COOL (Blue) to WARM (Red) causes a corresponding movement on the air temperature control door and determines the temperature that the system will maintain.

System uses a reheat method to provide conditioned air to the passenger compartment.

• All airflow from the blower motor (18527) passes through the A/C evaporator housing .
• Temperature is then regulated by reheating a portion of the air and blending it with the remaining cool air to the desired temperature.
• Temperature blending is varied by the air temperature control door, which regulates the amount of air that flows through and/or around the heater core (18476) , where it is then mixed and distributed.

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inside you plenum box:

There is a vacuum line that is operated by your selector switch, it is located under the hood, roughly in the center, up against the fire wall. If the line has leaks, your selector switch will not work and therefore your blower doors will not open and your heat will not be directed to the cabin of your vehicle. Replace the line.

There is a vacuum line that operates your selector switch, it is located under the hood, roughly in the center, up against the fire wall. If the line has leaks, your selector switch will not work and therefore all your blower doors will stay shut. Replace the line.

Yes it could be the switch but you should be able to reach up under the dash and manually switch the vents by hand