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2001 Ford Pickup 4.6L Eng F150
MANUAL HVAC SYSTEM - F150
OPERATION > CONTROL PANEL >
Temperature Control Knob >
Temperature control knob controls a blend door potentiometer which controls an electronic temperature
blend door motor. Temperature blend door motor provides a variable number of temperature blend door
positions. When temperature control knob is in COOL position, temperature blend door shuts off airflow to
heater core. When knob is in WARM position, air is directed through heater core. When knob is in
intermediate positions, heated air is blended with cooler incoming air to achieve desired temperature.
SYMPTOM TESTS > TEST A:
IMPROPER/ERRATIC AIRFLOW FROM OUTLETS
>
1. Start engine. Place blower motor switch in HI position. With engine at idle and under acceleration,
check for proper airflow from each mode switch position. If airflow is from defrost outlets only at all
speeds, go to next step. If airflow is from defrost outlets under acceleration, go to step . If airflow is
incorrect under one or more conditions, go to step . If airflow is okay under all conditions, system is
okay at this time.
2. Turn ignition off. Ensure Black vacuum supply hose is connected between engine intake manifold and
vacuum reservoir check valve. If hose is connected, go to next step. If hose is disconnected,
reconnect hose and retest system.
3. Disconnect vacuum supply hose. Plug vacuum hose at one end. Using vacuum pump, apply vacuum
to hose. If hose leaks, replace vacuum hose. Retest system. If hose does not leak, go to next step.
4. Start engine. Disconnect reservoir hose and control assembly hose from vacuum check valve. Check
for vacuum. If vacuum exists at both ports, go to step . If vacuum does not exist, go to next step.
5. Turn ignition off. Inspect vacuum check valve for obstruction and/or proper operation. Airflow through
valve should be in direction of engine (marked VAC). If valve is obstructed or plugged, replace valve
and retest system. If valve is okay, go to next step.
6. Turn ignition off. Disconnect all 3 vacuum hoses from vacuum check valve. With a "T" fitting and 2
hoses, attach check valve to vacuum pump. Apply 15 in. Hg of vacuum. If vacuum leaks down more
than 1 in. Hg per minute, remove check valve and plug vacuum hoses. Apply 15 in. Hg to ensure
tester and hoses are not cause of leak. If check valve loses more than 1 in Hg of vacuum per minute,
replace vacuum check valve. Retest system. If vacuum does not leak down more than 1 in. Hg per
minute, reinstall vacuum check valve and hoses and go to next step.
7. Disconnect vacuum reservoir tank. Connect vacuum tester to vacuum reservoir tank. Apply vacuum
and check for leak down. If reservoir leaks, replace vacuum reservoir assembly. Retest system. If
vacuum reservoir does not leak, go to next step.
8. Disconnect A/C-heater control vacuum supply hose. Attach vacuum tester and apply vacuum to check
for leaks. If Black supply hose leaks, replace hose and retest system. If supply hose does not leak,
remove plug and reconnect vacuum hose. Go to next step.
9. Disconnect vacuum harness in-line, multiple connector (near damper door switch). Plug all vacuum
hoses except Black supply hose. Select each function position on function selector switch while
applying 15 in. Hg of vacuum to Black hose. If vacuum drop exceeds 1 in. Hg per minute, note
positions where vacuum leak occurs. Go to next step. If system holds vacuum, reconnect in-line
vacuum harness and go to step .
10. Remove vacuum harness from function selector switch. Connect vacuum tester to control supply port
and plug control port that indicated a leak in previous step. Select appropriate function position and
apply 15 in. Hg of vacuum. Vacuum leak down should not exceed 0.5 in. Hg per minute. If vacuum
leak down exceeds specified rate, replace function selector switch. Retest system. If leak down does
not exceed specified rate, go to next step.
11. Disconnect damper door switch vacuum supply hose. Connect vacuum tester to supply hose and try
to pull a vacuum. If vacuum can be pulled, hose is plugged or restricted. Replace hose and retest
system. If no vacuum can be pulled, reconnect supply hose and go to next step.
12. Plug one end of suspect vacuum hose, as noted in step . Attach vacuum tester to other end and
apply 15 in. Hg of vacuum. If there is leakage at vacuum jumper harness connector, repair or replace
vacuum jumper harness. Retest system. If no leakage is noted, replace function selector switch.
Retest system.
13. Turn ignition off. If airflow system functioned properly prior to current complaint, go to step . If
airflow system did not function properly in the past, go to next step.
14. Individually check each vacuum hose. Connect vacuum tester to each hose and try to pull vacuum. If
vacuum can be pulled, hose is plugged or restricted. If hose is plugged or restricted, replace vacuum
hose and retest system. If vacuum cannot be pulled, go to next step.
15. Compare vacuum hose color in vacuum harness with each connector on function selector switch
vacuum connector. See . If hose colors of vacuum harness and connector colors match, go to next
step. If hose colors of vacuum harness do not match, replace vacuum harness. Retest system.
16. Check A/C vacuum circuit for pinched or kinked vacuum hose(s). See . If any hose is pinched or
kinked, reposition or replace hose and retest system. If hoses are okay, go to next step.
17. Check each vacuum hose to ensure it is properly attached at all connections. If any vacuum hose is
disconnected, reconnect hose and retest system. If hoses are properly connected, go to next step.
18. If any hose was suspect of leaks in any prior checks, disconnect suspect hose, plug one end and
attach vacuum tester to other end. Apply vacuum and check for leaks. If leak exists, repair or replace
hose. Retest system. If hose is okay, go to next step.
19. Disconnect hose from vacuum control motor. Apply 15 in. Hg of vacuum to vacuum control motor. If
vacuum drop exceeds 0.5 in. Hg per minute, replace vacuum control motor and retest system. If
vacuum drop is within limits, go to next step. Reconnect vacuum control motor hose.
20. Check attachment of vacuum control motor to damper door. If motor arm is properly attached to
damper door, service damper door for binding and retest system. If motor arm is not properly
attached to damper door, connect motor arm and retest system.