MODEL IDENTIFICATION
Adjustment and repair procedures in this article are referred to by series designation rather than by model name. Following table lists General Motors model name and series designation.
| Model | Designation |
|---|---|
| Blazer, Bravada, Jimmy, Pickup, Sonoma, Syclone & Typhoon | "S" & "T" Series |
GENERAL MOTORS MODEL DESIGNATION
DESCRIPTION
System is a blend-air type. Outside air is heated and then mixed with cooler outside air to attain desired temperature. System consists of a blower, air inlet assembly, heater air distributor assembly and heater control panel.
Blower, air inlet assembly and heater hoses are located on engine side of firewall; heater core and distributor duct are on passenger side. Coolant circulation keeps heater core hot at all times.
Operation of blower motor is controlled by fan switch. Motor is connected in series with fan switch and blower resistor assembly.
TEMPERATURE CONTROL LEVER
The left lever has maximum heat position at top and cool position at bottom.
MODE CONTROL LEVER
When lever is in VENT position (if equipped), all discharge air is directed to upper outlets. When lever is in DEF (defrost) position, most air is directed to windshield (defroster) outlets with some air directed to floor (heater) outlets. When lever is in HEATER position, most air is delivered through floor outlets with some air directed to windshield outlets.
BLOWER CONTROLS
Blower control can be knob or lever type. Controls run vertically with blower switch at top.
CONTROL CABLES
Remove cable retainer at heater, and remove cable. Bend control cable to lengthen or shorten cable. Install cable and retainer. Cycle control lever through its full range of travel. If necessary, readjust cable.
TROUBLE SHOOTING
Note. Also see the HEATER SYSTEM TROUBLE SHOOTING article in this section.
BLOWER MOTOR INOPERATIVE
- Turn ignition switch to RUN position. Set blower switch to HI position. Disconnect Orange wire at blower motor. Connect a test light from Orange wire at blower motor connector to ground. If test light does not glow, go to step 3). If test light glows, go to next step.
- Connect test light from Orange wire to Black wire at blower motor. If test light glows, replace blower motor. If test light does not glow, repair open in Black wire between blower motor and ground. See WIRING DIAGRAMS at the end of this article.
- Connect test light from Orange wire at blower switch connector to ground. If test light does not glow, go to step 4). If test light glows, repair open in wires between blower switch connector and blower resistor connector.
- Connect test light from Brown wire at blower switch connector to ground. If test light glows, replace blower switch. If test light does not glow, repair open in Brown wire between blower switch connector to fuse block.
BLOWER MOTOR OPERATES IN HI ONLY
- Turn ignition switch to RUN position. Set blower switch to position that DOES NOT operate. Connect test light from wire of inoperable blower switch position at blower resistor connector to ground. LO position is Yellow wire, and MED position is Light Blue wire.
- If test light does not glow, replace blower switch. If test light glows, disconnect blower resistor connector. Connect test light from either Yellow wire or Light Blue wire (depending on switch position) at blower resistor connector to ground. See WIRING DIAGRAMS at the end of this article.
- If test light does not glow, repair open in Yellow wire or Light Blue wire between blower resistor connector and blower switch connector. If test light glows, replace blower resistor.
Removal & Installation
Disconnect negative battery cable. Disconnect electrical connector at blower motor. Remove blower motor screws, and remove blower motor. (Scheme 1) To install, reverse removal procedure.
Scheme 1
- Disconnect negative battery cable. Remove screws from bottom of control panel. Pull control assembly away from instrument panel. (Scheme 2)
- Disconnect control cables and blower switch electrical connectors. Remove control assembly. Remove blower switch knob and retaining clip, and remove blower switch. To install, reverse removal procedure.
Scheme 2
HEATER CORE
| CAUTION | Heater core can be damaged if too much force is applied to heater core pipes during hose removal. |
- Remove the heater outlets and ducts from under instrument panel. Remove air distribution module assembly, heater assembly and seal. (Scheme 3), numbers 11-18.
- Disconnect negative battery cable. Drain engine coolant. Remove heater hoses at core. Remove rear case screws. Remove rear case. Remove heater core from front case. To install, reverse removal procedure. (Scheme 3) Fill cooling system, and check for leaks.
Scheme 3
Scheme 4
Scheme 5
Disconnect negative battery cable. Pull control assembly from dash. (Scheme 6) Disconnect cables at control assembly and heater assembly. Remove cables. To install, reverse removal procedure.
Scheme 6
See also:
• HEATER SYSTEM TROUBLE SHOOTING