Why on my 2003 expedition with manual temperature does the blower only work on max, or 4

Which of these two systems does your truck have?

Electronic Automatic Temperature Control (EATC) System
Or
Electronic Manual Temperature Control (EMTC) System


Electronic Manual Temperature Control (EMTC) System
The electronic manual temperature control (EMTC) system heats or cools the vehicle depending on the EMTC control panel selection.

• The EMTC control panel selections determine heating or cooling, air distribution and enables blower motor operation.
• The temperature control setting determines the air temperature.
• The blower motor switch varies the blower motor speed.
• During A/C operation the system also reduces the relative humidity of the air.

The EMTC system operation is determined by the settings on the climate control module. The EMTC system is composed of the EMTC module, blower motor resistor, mode door actuator, air inlet door actuator and temperature blend door actuator to control the various functions.
The blower motor switch:

• sets the blower motor speed.
• directs the blower motor path to ground through the blower motor resistor to allow blower motor operation in LO, MED LO and MED HI.
• directs the blower motor path directly to ground, bypassing the blower motor resistor, to allow blower motor operation in HI.

The A/C request button:

• can command the A/C compressor ON when the function selector switch is in PANEL, FLOOR/PANEL, FLOOR/DEFROST and FLOOR when the A/C request switch is pressed. Indicator illuminates when A/C request switch is toggled ON.
• is inoperative in MAX A/C, OFF and DEFROST.
• indicator illuminates when the function selector switch is in MAX A/C and cannot be toggled.
• indicator does not illuminate in OFF and cannot be toggled.
• indicator does not illuminate in DEFROST but can be toggled ON or OFF. The A/C compressor will operate regardless of indicator status if the outside air temperature is above 6°C (43°F).
• is serviced only with the EMTC module.

The function selector:

• selects airflow direction.
• is serviced only with the EMTC module.

The temperature selector:

• selects full warm and full cool as well as blended outlet temperatures.

The air recirculation button:

• selects either recirculated or outside air source.
• recirculates air in any mode except DEFROST, if requested.
• is disabled in MAX A/C or OFF mode where recirculated air only is used.
• is disabled in DEFROST mode where outside air only is used.
• is serviced only with the EMTC module.

The EMTC module also includes:

• a heated mirrior button. Refer to Section 501-09 .
• heated seat controls. Refer to Section 501-10 .

I will post and not cover Rear AUX heater box. ok, and is and option

what part of this car has blower
is this HVAC blower failing on HIGH
is this manual version or climate control option.
fuse are blown in cab or in bay (engine)
fuses are first of high speed blower mode fails dead.
what IS A CKED ????? is see no hits in my ASE books on that part or device name in a car or a truck
2003 chevy tahoe , no engine /trans told. (this dictates fuse boxes)
my guess HVAC topic but no sure, what fan/blower or turbo this is.
climate control model has left and right controls and all differenet wiring max. differ.
fuse Hvac1, hvac-ECas, and fuse BOWER< yes 3 fuse must not be blown and the BCM is the brain here.
not scanning the PCM to see BCM errors is a huge error in testing
manual controls the resistor block uses a relay to send 12dc to he blower set to HIGH. all resistors bad ,high still works.

here are the 4 things to fail;
4 is good so 3 things, 2 fuses,
#3 is relay. to fail. a volt meter finds this easy for sure reading this page in the SM.below 3 pins on relay are at 12v.
so are pin F and G 12vdc if not input to them is bad.
not counting bad wires.,

Check your rear resistors it could have the blower working it's back by the rear door remove cover should right there under blower motor

Under dash on passenger side is Blower Motor Resistor "wire harness plug" which is shorting. it's loose or was previously arcing and burnt up a little from heat. You can reshape the female pins to make the needle pins insert more tight. Or you should replace the Blower Motor Resistor harness if it's too far gone. ( it clips apart, usually a white plug just underneath glove box location. Sometimes is damaged by passengers feet. Your speed 1 thru 3 is resisted. Fan speed # 4 is max voltage and does not use the Resistor. I assume the resistor is shot ( located inside the clip coming from blower motor) or else there is a short on 1 of the wires female to male pins.

By 2003 most air-con systems had considerable electronic control and your problem might be caused by a malfunction there, wiring problems, compressor clutch problems or maybe there is a leak and the refrigerant pressure has already fallen to the point where the system is ceasing to work depending on temperature.

Here's a link,may be your coolant temperature sensor. P0125 OBD II Trouble Code Insufficient Coolant Temperature for Closed Loop... Here's a video of where it's at Coolant temperature sensor location 2003 Expedition 5 4

what year? for 2000, there are no control valves. It mixes a/c air with heater core air to blend the right temp.

SECTION 412-02: Heating and Ventilation 2000 Expedition/Navigator Workshop Manual
DESCRIPTION AND OPERATION Heating/Defrosting The heating and defrosting system has the following features:

• Controls the temperature and, during A/C operation, reduces the relative humidity of the air inside the vehicle.
• Delivers heated or cooled air to maintain the vehicle interior temperature and comfort level.
• Controls the A/C blower motor speed.
• Cooling or heating can be adjusted to maintain the desired temperature.
• Uses a reheat method to provide conditioned air to the passenger compartment.
• The blower motor draws outside air through the A/C recirculating air duct, except for MAX A/C cooling, when recirculated air is used.
• All airflow from the blower motor passes through the A/C evaporator core.
• The temperature is then regulated by reheating a portion of the air and blending it with the remaining cool air to the desired temperature.
• The temperature blending is controlled by the temperature blend door, which regulates the amount of air that flows through and around the heater core, where it is then mixed and distributed.

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Check the actuator motor on the heater if controls the doors that direct the heat and ac. It is an easy replacement part and as to the cost I wouldn't know but you can check price on line at autozone.

it maybe a door are something thats not opening i do not know but try these websites fix & troubleshoot heating & A/C www.automedia.com and the other one is car A/C repair www.directgardening.com and if all fails stop by your local library and get your hands on a haynes auto repair manual for your truck.

the squirrel cage is probably loose on the blower motor shaft.

here's 2003, don't have 04.

SECTION 412-02: Heating and Ventilation 2003 Expedition/Navigator Workshop Manual
REMOVAL AND INSTALLATION Blower Motor Removal and Installation

1. Remove the RH lower instrument panel insulator.

1. Remove the RH scuff plate.

1. Position the carpet aside.

1. Remove the blower motor.
   1. Disconnect the electrical connector.
   1. Remove the screws.
   1. Remove the blower motor.