Heater problem
2000 Ford F350 V8 Four Wheel Drive Automatic 200,00 miles

My heater fan only works on high. Also squeals every once in awhile when turned on. My question is how do I replace it. Is it done from the engine compartment or the under the dash. Does the dash have to be removed?

HEATER SYSTEMS - F250-F350 SUPER DUTY -2000 Ford Pickup F350 Super Duty
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TEST C: BLOWER MOTOR INOPERATIVE IN LOW
1.Disconnect blower motor resistor 4-pin harness connector C169. Turn ignition switch to RUN position. Place function selector switch to FLOOR position. Measure voltage between ground and blower motor resistor harness connector C169 terminal No. 1 (Orange/Black wire). See Fig. 4 . If more than 10 volts exists, go to next step. If 10 volts or less exists, repair open in Orange/Black wire between blower motor and blower motor resistor. See WIRING DIAGRAMS . Retest system. 2.Turn ignition off. Measure resistance of Black wire between ground and blower motor resistor harness connector C169. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in Black wire. Retest system. 3.Place blower switch in medium-low position. Measure resistance between ground and blower motor resistor harness connector C169 terminal No. 3 (Light Green/White wire). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, go to step 6 . 4.Place blower switch in medium-high position. Measure resistance between ground and blower motor resistor harness connector C169 (Yellow/Red wire). If resistance is less than 5 ohms, replace blower motor resistor. Retest system. If resistance is 5 ohms or more, go to next step. 5.Disconnect blower motor switch 4-pin harness connector C260. Measure resistance of Yellow/Red wire between blower motor switch harness connector C260 terminal No. 3 and blower motor resistor harness connector C169 terminal No. 2. See Fig. 3 and Fig. 4 . If resistance is less than 5 ohms, replace blower motor switch. Retest system. If resistance is 5 ohms or more, repair open or high resistance in Yellow/Red wire. See WIRING DIAGRAMS . Retest system. 6.Disconnect blower motor switch 4-pin harness connector C169. Measure resistance of Light Green/White wire between blower motor switch harness connector C260 terminal No. 4 and blower motor resistor harness connector C169 terminal No. 3. If resistance is less than 5 ohms, replace blower motor switch. If resistance is 5 ohms or more, repair open or high resistance in Light Green/White wire. See WIRING DIAGRAMS . Retest system.
Fig. 4: Identifying Blower Motor Resistor 4-Pin Harness Connector C169 Terminals
Courtesy of FORD MOTOR CO.


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10/4/2008


It is probably a bad blower resistor, but if the fan is noisy, it may need replacement as well. Both are under the hood, look for #1, thats the resistor.