Heater System Dodge Ram II

DESCRIPTION

All models use a blend-air system. Outside air enters heater through cowl opening and passes through a plenum chamber to heater core. A temperature control door in heater housing either directs incoming air through or around heater core.

Once past heater core, heated air and unheated air are mixed, producing air at desired temperature. Heater discharge is then directed through dash panel to air distribution duct in passenger compartment.

Van/Wagon may have optional auxiliary rear heater unit. Rear heater unit consists of a heater core and 3-speed blower motor enclosed in a housing. Rear heater unit is mounted on floor, behind driver's seat. Rear heater unit recirculates air inside vehicle.

Auxiliary rear heater unit's coolant flow control valve is engaged after instrument panel's temperature control lever is moved past its first quarter of travel. Auxiliary rear heater blower speeds are controlled by a separate 4-position toggle switch mounted on instrument panel, below heater controls.

HEATER CONTROL PANEL

Control panel contains temperature control lever; off, heat, bi-level, and defrost push button mode switches; and a 4-position fan switch.

Fan Switch

Four-position switch allows operation of fan at 3 different speeds. Lever-type switch has OFF, low, medium and HI (high) positions.

Mode Control Push Buttons

Mode push buttons are used to control airflow. There are 4 modes of operation: off, bi-level, heat, and defrost. Vacuum motors position mode door and heat/defrost door in air distribution duct. Doors direct air to panel outlets, heater, or defroster ducts. Vacuum switches control all doors except temperature blend/air door.

Temperature Control Lever

Control lever operates blend/air door. When in far left position, air by-passes heater core, producing cool air for ventilation. As lever is moved to right, blend/air door directs air through heater core to provide a mixture of unheated and heated air. In far right position, all air is directed through heater core, providing maximum heat.

TESTING

BLOWER MOTOR RELAY

1. Blower motor relay is located in Power Distribution Center (PDC). Rear blower motor relay is located behind instrument cluster, taped to wiring harness.
2. Remove relay, using a test light connected to ground, check for battery voltage at cavity No. 30 of PDC. (Scheme 1) If battery voltage is not present, check fuse No. 7 (25-amp) of passenger compartment fuse box. If battery voltage exists, go to next step.
3. Using an ohmmeter, check for continuity between terminals No. 87A and 30 of relay. (Scheme 1) If continuity does not exist, replace relay. Check that continuity does not exist between terminals No. 30 and 87. If continuity exists, replace relay. If continuity does not exist, go to next step.
4. Measure resistance between terminals No. 85 and 86 of relay. Reading should be 70-80 ohms. If reading is not as specified, replace relay. If reading is as specified, go to next step.
5. Using jumper wires, connect battery voltage to terminal No. 86 and ground terminal No. 85. (Scheme 1) Check that continuity exists between terminals No. 30 and 87. Check that continuity does not exist between terminals No. 87A and 30. If continuity is not as specified, replace blower motor relay. If continuity is as specified, relay is okay.

Scheme 1

REMOVAL & INSTALLATION

Remove auxiliary heater assembly. See AUXILIARY HEATER ASSEMBLY & HEATER CORE. Remove blower motor screws and remove blower motor from heater assembly. To install, reverse removal procedure.

1. Disconnect negative battery cable. Drain coolant from radiator. From under vehicle, disconnect auxiliary heater inlet and outlet hoses from heater core tubes. Remove heater assembly to floor mounting nuts.
2. From inside vehicle, disconnect blower motor connector and remove heater assembly. Remove heater cover screws. Heater core and cover are removed as a unit. Remove heater core from cover.To install, reverse removal procedure. Fill cooling system and check system operation.

1. Remove top half of radiator shroud. At right side of engine compartment, disconnect blower motor wiring connector and motor cooling tube.
2. Remove nuts and washers from blower motor backing plate to heater housing studs. (Scheme 2) Remove blower motor assembly.
3. Inside blower wheel, remove spring clip fastening blower wheel to blower motor. Inspect backing plate seal for breaks and adhesion. To install, reverse removal procedure.

Scheme 2

Removal & Installation (Front)

Blower motor resistor is located behind glove box attached to dash plenum panel. Disconnect negative battery cable. Remove glove box bin. Disconnect blower motor resistor connector. Remove resistor retaining screws. Remove blower motor resistor. To install, reverse removal procedure.

Removal & Installation (Rear)

Blower motor resistor is integral to the rear blower motor. If resistor is faulty, rear blower motor must be replaced. See AUXILIARY BLOWER MOTOR .

1. Disconnect negative battery cable. Remove 2 heater control panel bezel screws. Remove bezel enough to disconnect switches and cigarette lighter wiring. Remove heater control panel screws.
2. Pull control panel outward enough to disconnect electrical connectors, vacuum connector, and control cable. Remove heater control panel. To install, reverse removal procedure. Adjust control cables as required. See «TEMPERATURE CONTROL CABLE»(/dodge/ram/ii-1994-2001/remont/heater/#heater-system) .

1. Disconnect negative battery cable. Drain engine cooling system. In engine compartment, protect generator from coolant spillage, remove heater hoses from heater core tubes.
2. Disconnect temperature control cable from heater housing cover. (Scheme 2) Remove grille, cowl grille support panel, right headlight assembly, and right radiator core support assembly. (Scheme 3) From inside vehicle, remove glove box bin. Through glove box opening and from under instrument panel, remove nuts and bolts attaching heater unit to dash panel.
3. Remove blower housing flange screws. Separate heater assembly from blower housing. (Scheme 2) Carefully remove heater assembly from vehicle. Remove heater housing top cover. Remove heater core tube strap screw. Remove heater core.
4. To install, reverse removal procedure. Ensure heater housing top cover seal, firewall and side cowl seals are in good condition.

Scheme 3

Scheme 4

Removal

Disconnect temperature control cable from heater housing. Remove self-adjusting clip. (Scheme 2) Remove heater control panel. See CONTROL PANEL. Depress cable flag locking tab and remove cable from control panel. Pull cable through dash panel into passenger compartment.

Installation

1. Install cable through dash panel from passenger compartment side. Ensure cable is properly routed. On control panel, slide cable core wire loop end onto temperature control lever pin and snap flag into receiver. Install retaining nut over cable end on temperature control lever. Install control panel.
2. Pull cable housing from engine compartment side, until cable grommet is seated in dash panel. Position self-adjusting clip on core wire about 2" from loop end of temperature control cable. Using tube or rod, pry clip into locked position. (Scheme 5) Place self-adjusting clip over blend/air door crankpin. Snap cable into retaining clip.
3. Locating tape should be next to side of clip farthest from crank arm. Adjust cable by moving temperature control lever to full right (warm) position.

Scheme 5

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 6

Scheme 7

Scheme 8

See also:
• AUXILIARY BLOWER MOTOR