What fuse powers the heater blower motor?

Power to the heater blower circuit is through fuse 3, rated 35a, hot when the ignition switch is in Run or Accy.

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

Make sure the ignition switch is in RUN or ACCY, check fuse 3, and check for power at the blower switch connector. If there is no power, repair the feed to the connector; if there is power, turn the switch to HIGH and check terminal 4 of the blower motor resistor pack.

Where is the blower motor resistor located?

Per the component table, the blower motor resistor is in the RH blower housing; the blower motor itself is in the engine compartment at the RH dash panel.

What are the positions of the heater blower switch?

It is a 4-position switch: 1) Off, 2) Low, 3) Med, 4) Hi.

What wire colors are used in the heater blower circuit?

Orange (o) feeds through fuse 3 to the switch; r/bk goes to resistor terminal 1, bl/r to terminal 2, bk/y for the high-speed feed and to the blower motor via connector C605, and black (bk) from the motor to ground G601.

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1979 Ford Bronco/F100-F350 Heater Blower Motor Wiring Diagram & Troubleshooting

Ford truck heater-only electrical system wiring diagram and blower troubleshooting through fuse 3

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Reference · 1978-1979 BroncoAll 116 wiring diagrams

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Heater-only blower wiring: 4-position blower switch and resistor pack fed through fuse 3 vary motor speed; includes terminal 3/4 diagnostic checks and a wiring diagram with connector table.

Part of 1978-1979 Ford Bronco Wiring Diagrams

AI caption August 2014 · Photo 40 of 48

This page (page 40) from a Ford Bronco/F100-F350 electrical reference manual explains the Heater Only Electrical System. It describes how the system works: with the ignition switch in RUN or ACCY, the blower motor circulates heater air and is controlled by a 4-position switch (Off, Low, Med, Hi) that sends full voltage for high speed and reduced voltage through a resistor pack for lower speeds, with power supplied through fuse 3 (35 amp). A detailed trouble-shooting flow covers two failure modes: blower fails in all switch positions (check fuse 3, power at the blower switch connector, terminals 3 and 4 of the resistor pack, and the switch feed wire) and blower operates in only one or two positions (test power at resistor pack terminals 1, 2, and 3 at Low/Medium/High, check switch continuity, replace the resistor pack or switch as needed). A wiring schematic shows the circuit from fuse 3 through the heater blower switch, blower motor resistor pack, connector C605, blower motor, and ground G601, with wire colors (orange, red/black, blue/red, black/yellow, black). A component table lists locations for the blower motor, resistor, connectors C605/C613/C616, splices S603/S701, and ground G601.

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Frequently asked questions

What fuse powers the heater blower motor?: Power to the heater blower circuit is through fuse 3, rated 35a, hot when the ignition switch is in Run or Accy.
What should I check if the blower motor doesn't work in any switch position?: Make sure the ignition switch is in RUN or ACCY, check fuse 3, and check for power at the blower switch connector. If there is no power, repair the feed to the connector; if there is power, turn the switch to HIGH and check terminal 4 of the blower motor resistor pack.
Where is the blower motor resistor located?: Per the component table, the blower motor resistor is in the RH blower housing; the blower motor itself is in the engine compartment at the RH dash panel.
What are the positions of the heater blower switch?: It is a 4-position switch: 1) Off, 2) Low, 3) Med, 4) Hi.
What wire colors are used in the heater blower circuit?: Orange (o) feeds through fuse 3 to the switch; r/bk goes to resistor terminal 1, bl/r to terminal 2, bk/y for the high-speed feed and to the blower motor via connector C605, and black (bk) from the motor to ground G601.