Heater Blower Controls Circuit Description. GMC Truck Jimmy

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 Jimmy - 2WD 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Heater Blower Controls Circuit Description

Voltage is supplied to the heater controller by the HVAC fuse 9. Power to the blower motor is supplied through the mode selector switch in any of the following positions:

•

DEF

•

BLEND

•

HEAT

•

VENT

•

BI-LEVEL

Splice S215 splits the power source between the blower motor resistor and the blower switch. Voltage is always present at cavity B of the blower motor resistor when the mode selector switch is in one of the mode positions.

In the low position, voltage passes through the following components:

•	All 3 of the resistors

•	The blower motor relay

•	The blower motor

The following actions occur in the MEDIUM 1 mode:

•	The current is reduced through the 2 blower motor resistors.

•	The fan speed decreases.

The following actions occur in the MEDIUM 2 mode:

•	The current goes through 1 resistor. The current is increased.

•	The fan speed increases.

In the HIGH mode, the current bypasses the blower motor resistor and energizes the blower motor relay. The relay supplies the full battery voltage to the blower motor through the HVAC fuse in the underhood bussed electrical center (UBEC). Ground is provided at G117.