What fuse protects the heater/AC blower circuit and what is its rating?

Fuse 3, rated 35 Amps; it is hot when the ignition switch is in RUN.

What should I check first if the blower motor doesn't work in any switch position?

Check fuse 3, verify the ignition switch is in the RUN position, and check the feed to fuse 3.

What wire colors run to the blower motor resistor connector C604?

Wire 270 (bk/y), wire 269 (bl/r), and wire 268 (r/bk).

Where is the blower motor located?

In the engine compartment, at the RH dash panel; the blower motor resistor is on the RH blower housing.

What are the A/C function control switch positions?

1) Off, 2) Vent, 3) A/C, 4) Hi/Lo, 5) Heat, 6) De-fog, 7) Defrost.

What does the note about two blower switch types mean?

Two types of blower switches were used; terminal identification is on the connectors. One type uses codes like B-M1, the other uses numeric codes like (2)-(5).

Home/ Registry/ Ford/ Bronco/ 1978-1979/ 1979 Ford Bronco/ Photo supermotors.net/registry/media/1032660

1979 Ford Bronco/F100-F350 Heater & A/C Electrical System Wiring Diagram

Ford truck heater and air conditioner electrical wiring diagram with blower resistor connector chart

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Heater/AC electrical wiring: blower motor, compressor clutch coil, de-icing switch, resistor pack through fuse 3; includes blower-speed continuity chart for wire 270 (bk/y) at connector C604.

AI caption August 2014 · Photo 41 of 48

This is page 41 of a Ford electrical reference guide (uploaded as part of a 1979 Bronco / F100-through-F350 set), covering the Heater and Air Conditioner Electrical System. It explains that the A/C-heater system has six basic electrical components: blower motor, compressor clutch coil, de-icing switch, blower speed switch, blower motor resistor, and the system OFF-ON/clutch switch. A detailed trouble-shooting flow addresses a blower motor that does not run in any position (check fuse 3, a 35-amp fuse hot when the ignition is in RUN), a blower working in only some speeds (checking wires 270 bk/y, 268 r/bk, and 269 bl/r at resistor connector C604), and a compressor clutch that does not engage. A full-page schematic shows the circuit from Fuse 3 through the A/C function control switch (Off, Vent, A/C, Hi/Lo, Heat, De-fog, Defrost), blower switch, resistor pack, de-icing switch, A/C clutch solenoid, and blower motor, with wire colors and connectors C604, C605, C613, C616, splices S603/S701, and ground G601. Tables list blower switch continuity connections by speed and component locations, plus a note that two types of blower switches with different terminal codes were used.

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Frequently asked questions

What fuse protects the heater/AC blower circuit and what is its rating?: Fuse 3, rated 35 Amps; it is hot when the ignition switch is in RUN.
What should I check first if the blower motor doesn't work in any switch position?: Check fuse 3, verify the ignition switch is in the RUN position, and check the feed to fuse 3.
What wire colors run to the blower motor resistor connector C604?: Wire 270 (bk/y), wire 269 (bl/r), and wire 268 (r/bk).
Where is the blower motor located?: In the engine compartment, at the RH dash panel; the blower motor resistor is on the RH blower housing.
What are the A/C function control switch positions?: 1) Off, 2) Vent, 3) A/C, 4) Hi/Lo, 5) Heat, 6) De-fog, 7) Defrost.
What does the note about two blower switch types mean?: Two types of blower switches were used; terminal identification is on the connectors. One type uses codes like B-M1, the other uses numeric codes like (2)-(5).