Heater assembly is contained in housing beneath instrument panel. Assembly consists of blower motor, heater housing and core, water valve, and control panel. Control panel has mode, temperature, ventilation and blower controls.
Air doors (intake, blend air, heat, vent and defroster) are used to accomplish selected functions. Fan switch electrically controls blower speeds and is actuated through ignition switch and resistor.
VENTILATION
Ventilation is a separate function from heating and is combined into heating unit to accomplish fresh air ventilation when required. Separate selector lever or position setting on mode lever permits fresh air to be taken in through intake air door and into passenger compartment. Blower switch position determines air flow volume.
MODE LEVER
Mode lever controls air flow air doors (intake, blend-air, heat, defrost and ventilation). Lever position on control panel determines the flowing door settings
Air Intake Door
In open position, outside air flows into heater system after passing through blower motor fan. In closed position, inside air is recirculated through heater system.
Recirculated air is used to prevent outside air from entering passenger compartment (such as smoke, odors, etc.) or to allow faster heater warmup of passenger compartment on cold days.
Heat Door
Directs air to floor and defroster outlets when "HEAT" mode setting is selected.
Ventilation Door
Permits air flow out of panel registers.
Defroster Door
Controls air delivery or defroster outlets when this mode is selected. This separate door opens when mode door closes off floor and instrument panel outlets to direct air to windshield.
Blend Air Door
See TEMPERATURE LEVER operation below.
TEMPERATURE LEVER
This lever sets position of blend-air door to direct flow of air through heater core ("HOT" position), around heater core ("COLD" position), or mixture of both (modulated temperature between full "HOT" and full "COLD").
The lever also control opening and closing of water valve. In any position except "COLD", water valve is open, allowing engine coolant into heater.
FAN SWITCH
A separate sliding lever on control panel provides various fan speeds and is actuated through blower resistor.
Set air intake lever at "RECIRC" position. Connect cable to air intake door lever, then position door in its fully closed position. Push cable away from door lever to remove slack and secure with retaining clip.
BLEND AIR DOOR/TEMPERATURE CONTROL DOOR
- Set temperature lever to maximum "COLD" position. With air mix door moved away from link lever, connect temperature control rod to link lever and clamp cable. (Scheme 1)
- Pull control rod of water valve in direction of arrow so as to make clearance of about.08" (2.0 mm) between ends of rod and link lever and connect rod to door lever. Check knob to see if it moves smoothly.
Pulsar & Sentra Temperature Control Door Adjustment Pull control rod in direction of arrow. Scheme 1
MODE SELECTOR DOOR & HEAT-DEFROST DOOR
Note. After adjustments are complete, check all controls, doors, cables and rods for smooth and complete operation.
Pulsar & Sentra
Set mode selector lever to "DEF" position. Connect control cable to side linkage while pushing linkage upward. Pull cable in opposite direction to remove slack and secure with retaining clip. Stanza
NO HOT AIR DISCHARGED
Malfunctioning engine coolant thermostat. Heater core plugged. Low coolant level. Blend air door malfunctioning. Heater valve not opening.
NO AIRFLOW TO FLOOR
Blower motor speed too low. Poor electrical connection. Resistor or rheostat amplifier malfunctioning. Floor air door or floor air door actuator malfunctioning.
COLD AIR ONLY TO DEFROSTER
Malfunctioning engine coolant thermostat. Heater core plugged. Low coolant lever. Defroster or blend-air door malfunctioning. Heater valve not opening.
LOW AIRFLOW TO DEFROSTER
Floor/defroster door malfunctioning. Faulty door seal. Defroster nozzle plugged. Leaking duct-to-nozzle connection. Malfunctioning defroster door actuator.
HOT AIR AT ALL TIMES
Water valve not closing. Mode door malfunctioning. Mode door seal faulty.
NO BLOWER MOTOR OPERATION
Fuse blown or fusible link melted. Electrical lead to motor disconnected. Fan switch malfunctioning. Blower motor malfunctioning. Blower control amplifier malfunctioning. Resistor malfunctioning. Heater relay malfunctioning.
CONTROL LEVER DIFFICULT TO OPERATE
Inner wire rubbing on outer case end. Cable kinked or bent. Doors or lever sticking.
OUTSIDE AIR ENTERING WHEN FAN IS OFF
Air intake door misadjusted. Control cable misadjusted. Malfunctioning air intake door actuator.
BLOWER MOTOR/FAN NOISE
Loose bolt or foreign objects in blower fan. Broken blower fan blade(s).
Removal & Installation
Disconnect battery. Detach blower harness connector. Disconnect control cable from air intake door. Remove blower motor retaining screws and take out blower motor. To install, reverse removal procedure.
Removal (Pulsar & Sentra)
Remove control cables by unfastening clamps at door levers. Disconnect harness connector. Remove heater control mounting bolts and remove heater control assembly.
Installation
To install, reverse removal procedure. Adjust cables and rods and check system operation.
Exploded View of Van Heater Assembly. Scheme 2
Exploded View of 200SX Heater Assembly. Scheme 3
Exploded View of Pulsar NX & Sentra Heater Assembly. Scheme 4
Exploded View of Stanza & Stanza Wagon Heater Assembly. Scheme 5
HEATER CORE & ASSEMBLY
Note. Heater core Removal & Installation procedures are not available from manufacturer. However, an exploded view of the system has been provided.
Removal & Installation (Pathfinder & Pickup)
- Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Set temperature lever to HOT position and drain engine coolant. Disconnect inlet and outlet hoses from evaporator. Remove tube mounting bolt and rubber grommet. Plug all openings to evaporator. Disconnect heater hoses at firewall.
- Remove 4 bolts securing evaporator, disconnect thermo control amplifier 4-pin connector and remove evaporator. Remove instrument panel. See «INSTRUMENT PANEL»(/nissan/stanza/ii-1986-1989/remont/heater/#heater-system__instrument-panel) . Remove center brace assembly. Remove upper and lower air flow ducting. Disconnect heater control cables. Remove 3 securing screws from heater assembly case and remove assembly from vehicle. Separate case assembly and remove heater core. To install, reverse removal procedure. Bleed cooling system and recharge A/C system. See appropriate COOLING SYSTEM article. See appropriate AIR CONDITIONING SYSTEM in A/C-HEATER SYSTEM article
Exploded View Of (Pathfinder & Pickup) Heater Assembly. Scheme 6
Set temperature lever to "HOT" position and drain engine coolant. Disconnect heater hoses at engine compartment. Remove cluster lid, glove box, heater control panel and trim pieces. Remove heater unit assembly. To install, reverse removal procedure. Adjust cables and check system operation
INSTRUMENT PANEL
- Disconnect negative battery cable. Remove glove box. Remove 4 bolts and 2 screws from support plate. Remove radio bezel and radio. Remove trim cover from below radio. Remove heater controller knobs by pulling straight out from controller. Remove heater controller face plate by using a suitable tool pry on corners of faceplate. Remove 3 screws securing heater controller to instrument panel. Remove heater controller cables and remove controller.
- Remove steering wheel. Remove upper and lower steering column covers. Remove lower instrument panel trim cover for steering column. Open fuse panel and remove fuse block, once fuse block is removed, disconnect instrument panel Super Multiple Junction (SMJ). Using a suitable tool, pry up defroster grilles. Remove 8 instrument retaining bolts, 4 from under defroster grilles, 2 under corners of instrument panel and one on each side of instrument panel. To install, reverse removal procedure.
Scheme 7
See also:
• TEMPERATURE LEVER
• INSTRUMENT PANEL