GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 TopKick C-Series Commercial (Cutaway) C4/C5 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Schematics
Figure 1:

Heat Only
Object Number: 799888 Size: FS
Master Electrical Component List
Air Delivery Description and Operation
Blower Controls (C60)
B+ Bus Bar
Ignition Switch, RUN and ACC/RUN Bus Bars
BRAKE, CHASSIS, HTR/AC, and AXLE/4WD Fuses/Circuit Breakers
Interior Dimming Lamps System
G103 - 1 of 2, G105, and G106
G103 - 1 of 2, G105, and G106
G103 - 1 of 2, G105, and G106
G112, G113, G203 - 4 of 4, G204, G205 and G400
Figure 2:

Blower Controls (C60)
Object Number: 799891 Size: FS
Master Electrical Component List
Air Delivery Description and Operation
A/C Compressor Controls (C60)
Heat Only
B+ Bus Bar
Ignition Switch, RUN and ACC/RUN Bus Bars
BRAKE, CHASSIS, HTR/AC, and AXLE/4WD Fuses/Circuit Breakers
Interior Dimming Lamps System
A/C Compressor Controls (C60)
G103 - 1 of 2, G105, and G106
G103 - 1 of 2, G105, and G106
G103 - 1 of 2, G105, and G106
G112, G113, G203 - 4 of 4, G204, G205 and G400
Figure 3:

A/C Compressor Controls (C60)
Object Number: 799892 Size: FS
Master Electrical Component List
Air Delivery Description and Operation
Auxiliary Controls (C36)
Blower Controls (C60)
Ignition Switch, RUN and ACC/RUN Bus Bars
B+ Bus Bar
BRAKE, CHASSIS, HTR/AC, and AXLE/4WD Fuses/Circuit Breakers
Blower Controls (C60)
G100 (L18)
G100 (LB7)
G100 (LG4)
G100 (LG5)
Figure 4:

Auxiliary Controls (C36)
Object Number: 799893 Size: FS
Master Electrical Component List
Air Delivery Description and Operation
A/C Compressor Controls (C60)
Ignition Switch, RUN and ACC/RUN Bus Bars
Underhood Fuse Block, I/P Fuse Block, BATT/HAZ Fuse, PWR ACCY, HAZARD, TRLR TRN/HAZ, and STOP Fuses/Circuit Breakers
BRAKE, CHASSIS, HTR/AC, and AXLE/4WD Fuses/Circuit Breakers
Underhood Fuse Block, I/P Fuse Block, BATT/HAZ Fuse, PWR ACCY, HAZARD, TRLR TRN/HAZ, and STOP Fuses/Circuit Breakers
G102 - 2 of 2