Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1998ENVOY 2WD V6-4.3L VIN WREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGDESCRIPTION AND OPERATIONHEATING AND VENTILATION SYSTEM (WITH A/C)CIRCUIT DESCRIPTIONBLOWER CONTROLS
1998 GMC Envoy 2WD V6-4.3L VIN W
Blower Controls
1998 GMC Envoy 2WD V6-4.3L VIN WSECTION Blower Controls
Voltage is supplied to the heater and the air conditioning (A/C) controller by HVAC fuse 9. Power to the blower motor is supplied through the mode selector switch when the switch is in one of the following positions:
- DEF
- BLEND
- HEAT
- VENT
- BI-LEVEL
- NORM
- MAX A/C
S215 splits the power source between the blower motor resistor and the blower switch. When the mode selector switch is in one of the powered positions, power will always be present at cavity B of the blower motor resistor.
In the low position, voltage passes through all 3 resistors in the blower motor resistor through the blower motor relay and to the blower motor.
In MEDIUM 1, voltage passes through 2 resistors. In MEDIUM 2, voltage goes through 1 resistor. The HIGH position supplies trigger voltage to the blower motor relay. This condition energizes the blower motor relay and supplies full battery voltage to the blower motor through the HVAC fuse 38 in the underhood bussed electrical center (UBEC). Ground is provided at G117.
- DEF
- BLEND
- HEAT
- VENT
- BI-LEVEL
- NORM
- MAX A/C
S215 splits the power source between the blower motor resistor and the blower switch. When the mode selector switch is in one of the powered positions, power will always be present at cavity B of the blower motor resistor.
In the low position, voltage passes through all 3 resistors in the blower motor resistor through the blower motor relay and to the blower motor.
In MEDIUM 1, voltage passes through 2 resistors. In MEDIUM 2, voltage goes through 1 resistor. The HIGH position supplies trigger voltage to the blower motor relay. This condition energizes the blower motor relay and supplies full battery voltage to the blower motor through the HVAC fuse 38 in the underhood bussed electrical center (UBEC). Ground is provided at G117.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.