I have a 5.7 motor the heater works on the floor not on defrost what could the problem be

Item Part Number Description 1 18A318 Vacuum Control Motor-, Panel/Defrost Door 2 18A478 Panel/Defrost Door (Full Vacuum Position) 3 - Defrost Air Flow 4 - Side Window Demister Air Flow 5 18B545 Temperature Blend Door (Full Heat Position) 6 19860 A/C Evaporator Core 7 19A813 Air Inlet Duct Door (Full Vacuum Position) 8 - Outside Air Inlet 9 18A318 Vacuum Control Motor-, Air Inlet Duct Door 10 - Recirculated Air Inlet 11 18527 Blower Motor 12 19A566 A/C Vacuum Reservoir Tank and Bracket 13 - Vacuum from the Engine Intake Manifold 14 19B888 A/C-Heater Function Selector Switch 15 - Vacuum to the 4x4 Hub Solenoids 16 18495 Water Diverter Valve (Full Vacuum Position) 17 18476 Heater Core 18 18A559 Floor/Panel Door (Full Vacuum Position) 19 - Floor Air Flow 20 18A318 Vacuum Control Motor-, Floor/Panel Door 21 - Panel Vent Air Flow

I'd have to check actuator movement for defrost. The actuator is electric according to my database. The actuator should be under dash at end of hvac housing.

either the heater control or the lil motor that adjusts the door is shot.
i believe the motor is on top of the heater box behind the radio for the vent function there is also a blend door motor on the side (hot to cold) of the heater box.unplug the vent motor cycle the defrost/ floor knob and test for power . no power bad heater control .power present bad vent door motor. auto wreckers are the best place for these parts (cheapest) some will also test/ install

check the actuator motor on the heater sounds like the motor is not directing the air as it should. The motor is in the center of the truck inside attached to the heater and has arms on it to move the heater and ac doors.

. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ?
Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
• The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
• Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch (18578).
• The position of the function selector knob determines the manner in which the system will operate.
• Each position of the function selector knob is detented for positive engagement.
• Vacuum Control Motors The vacuum control motors (18A318):
  
  • are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
  • direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
  • The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).
  
  

The heater blend door actuator (motor) is faulty.Replace actuator

Could be faulting acutar motor for the hot air door. (1) Heater Core Cover (2) Heater Core (3) A/C Defroster Seal (4) Upper HVAC Module Case (5) Dash Seal (6) A/C Valve (7) Heater/Defroster Valve (8) Temperature Valve (9) A/C Valve Lever (10) Mode Valve Actuator (11) Heater/Defroster Valve Lever (12) Mode Valve Cam (13) Lower HVAC Module Case (14) Rear Heater Duct Seal (15) Temperature Valve Actuator Screw (16) Temperature Valve Actuator (17) HVAC Module Wiring Harness (18) Blower Motor Resistor/Relay Assembly (19) Blower Motor Acoustic Insulator (20) Blower Motor (21) Blower Motor Fan (22) Passenger Compartment Air Filter Access Door (23) Dash Seal (24) Evaporator Block Seal (25) Evaporator Core (26) Passenger Compartment Air Filters (27) Air Inlet Valve (28) Air Inlet Housing (29) Air Inlet Housing Seal (30) Air Inlet Actuator (31) Heater Core Pipe Seal

blend door motor on heater box needs replace or at least checked

When the engine is cold,check the coolant level.

Make sure it's on max.

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A coolant system should be flush every two years.

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If you did a coolant flush recently then air pocket can be the cause of the un-even heating problem.

The DIY method is to drive you car onto a ramp or a steep hill.

Iet the engine cool off and top off the coolant tank.

Set MAX heat + MAX fan

Let the engine ran for 20 minutes wih the cap off and the trap air will escape from the coolant reserve tank,

Check coolant level and top off coolant when the engine cools down.



A shop will charge $75+ for this but using an air operated excavate tool!

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A car with over 90K miles may experience linkage problem to the heater control valve.

The heater control valve (near the firewall) may be stick over time.

Open the hood and move the heater to max and min. Back and forth.

Clean and lube the linkage with WD-40 to free the heater control valve.

If it's a vacuum type heater control valve then cash for leaky vac. hoses.


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Move the fan switch back and forth to re-new the electrical conductors.

Pass a vacuum over the control panel to prevent dust build up behind the console.

Some times you can "reset" the computer for that by disconnecting the battery for 15 or 20 seconds then re-connecting it. If that doesn't work then the mode door motor assy might have stripped gears or broken gears. (they are plastic) If you are familiar with where the mode door motor assy is you can turn the knob to change the mode (i.e. defrost, panel, floor) and see if the motor is turning. If motor is turning and mode does not change then the plastic pieces have broke or stripped. Usually when there is a problem with the climate control system it will default to the defrost simply as a safety thing. So you will have defrost so you can see where you are going. Hope this helps you all out, good luck.