The heater control valve sits in the inbound heater hose on your Nissan Sentra. The valve connects to the heater controls in the dash of the car with a steel cable that opens and closes the valve as the temperature adjustment is made in the car. The valve is used to limit the flow of hot coolant through the heater core, changing the temperature of the air passing through it. A replacement valve is available at any auto parts store or through the dealer.
Open the hood of your Nissan and disconnect the negative battery cable from the battery terminal with a wrench. Remove the cable and isolate it from the battery.
Place a drain pan under the front of your Sentra on the passenger’s side of the radiator. Open the drain petcock in the radiator and drain the coolant until it is below the level of the heater hose. Opening the radiator cap and looking into the radiator will allow you to monitor the level of the coolant as you drain it.
Locate the two hose clamps on either end of the heater valve in the heater hose. Loosen both clamps with a flat head screwdriver and slide them away from the valve. Pull the hose off each end of the valve then disconnect the actuator cable from the valve control. Discard the old valve.
Push the heater hose ends on the heater control valve then slide the clamps onto the hose near the valve. Tighten the hose clamps with a flat head screwdriver until they are snug but do not crush the hose. Attach the control cable from the heater control onto the arm of the heater control valve by sliding the cable end into the hole in the arm.
Fill the cooling system with clean coolant; if the old coolant is clean, you may reuse it. Then attach the negative battery cable to the negative battery terminal and secure the mounting bolt with a wrench. Start the engine and allow it to run until it reaches normal operating temperature.
Position the heater control to “Hot” and turn the blower on high. Allow the engine to run while you check the coolant level. Continue to add coolant until the system is full and you are getting hot air out of the heater.
Close the radiator cap and shut off the engine. Check for leaks around the valve and tighten the clamps if necessary.
