Mechanics

HEATER NOT BLOWING WARM AIR

2000 Ford F-150 • 6 cylinder 2WD Automatic •

I have a 2000 ford f150 and the heater stopped working. It blows cold air out, but never gets warm, could it be something other than the heater core
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Jokersma
December 28, 2010.




Antifreeze level low, thermostat, Temperature blend door on the plenum stuck. Feel the heater hoses, they should both be HOT to the touch. If one is cold, heater core is clogged, if both are cold, thermostat or low on antifreeze.
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Merlin2021
Dec 28, 2010.
If both are hot, blend door is stuck.


Merlin2021
Dec 28, 2010.
What is a blend door and where is it


Tiny
Jokersma
Dec 28, 2010.
Blend door and the blend door actuator are located on the heater case(plenum)
TEST E: NO OPERATION IN ALL TEMPERATURE SETTINGS
Start engine and bring to normal operating temperature. Turn blower motor switch to LO
position. Turn mode selector switch to PANEL position (MAX A/C position, if A/C
equipped). Turn temperature control **** to full COOL position and check for cool air
discharge. Turn temperature control **** to full WARM position and check for warm air
discharge. Rotate temperature control **** from full WARM position to full COOL
position. If air temperature does not change, go to next step. If air temperature changes,
system is operating properly at this time.
1.
Turn ignition off. Remove fuse No. 5 (15-amp), located in Central Junction Box (CJB).
Check fuse condition. If fuse is okay, go to step 4. If fuse is blown, replace fuse and recheck
system operation. If fuse blows again, go to next step.
2.
Ensure ignition switch is off. Disconnect electronic blend door actuator 8-pin harness
connector C229. Disconnect temperature control switch (potentiometer) 4-pin harness
connector C217. Disconnect CJB 34-pin harness connector C242 (located under left side of
instrument panel). Measure resistance between ground and CJB connector C242 terminal
No. 15 (Light Blue/Pink wire). See Fig. 6. If resistance is more than 10 k/ohms, replace
CJB. If resistance is 10 k/ohms or less, repair short to ground in Light Blue/Pink wire
between CJB and electronic blend door actuator. See WIRING DIAGRAMS. Turn ignition off. Disconnect electronic blend door actuator 8-pin harness connector C229.
Turn ignition switch to RUN position. Measure voltage between ground and blend door
actuator connector C229. If more than 10 volts exist, go to next step. If 10 volts or less
exists, repair open in Light Blue/Pink wire between CJB and electronic blend door actuator.
See WIRING DIAGRAMS.
4.
Turn ignition off. Disconnect electronic blend door actuator control switch 63-pin harness
connector C220. Measure resistance of specified circuits between electronic blend door
actuator harness connector C229 and blend door actuator control switch harness connector
C220. See TEMPERATURE CONTROL SWITCH CIRCUIT IDENTIFICATION table. See Fig. 7. If resistance is less than 5 ohms for all wires, go to next step. If resistance
is 5 ohms or more on any wire, repair appropriate wire(s).
TEMPERATURE CONTROL SWITCH CIRCUIT IDENTIFICATION
Measure resistance between temperature control switch terminals No. 2 (Yellow/Light
Green wire) and No. 3 (Red/Light Green wire). See Fig. 7. Temperature control switchresistance should be more than 3000 ohms in full WARM position and less than 300 ohms in
full COOL position. Resistance should change gradually as temperature control switch ****
is turned from COOL to WARM and back. If switch resistance is as specified, go to next
step. If temperature control switch resistance is not as specified, replace temperature control
switch.
Measure resistance of Black wire between ground and electronic blend door actuator harness
connector C229 terminal No. 8. See Fig. 7. If resistance is less than 5 ohms, replace
temperature blend door actuator. If resistance is more than 5 ohms, repair Black wire
between ground and blend door actuator.
7.
COMPONENT TESTS
WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all SERVICE PRECAUTIONS and DISABLING &
ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM
SAFETY article in GENERAL SERVICING.


Merlin2021
Dec 28, 2010.

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