this should help you
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HEATER/VENT MODULE REPLACEMENT REMOVAL PROCEDURE
this is all i have on this one..i will opt out,mabe one of the other guys has a better instruction sheet
Maybe this will help.
2003 Chevrolet Silverado 3500
Heating, Ventilation, & Air Conditioning > Auxiliary Heating & Air Conditioning > Heater Core > Removal & Installation
Drain the engine coolant.
Remove the right rear quarter trim panel.
Remove the right rear wheelhouse.
Disconnect the auxiliary heater hoses from the heater core.
Disconnect the electrical connectors, as necessary.
Remove the drain valve (3).
Remove the bolts (1)
Remove the nuts (2, 4).
Remove the heater module.
Remove the blower motor, if necessary.
Remove the heater case cover.
Remove the heater core.
Auxiliary heater core housing
Install the heater core.
Install the heater case cover.
Install the blower motor, if necessary.
Install the heater module.
Install the nuts (2, 4).
Install the bolts.
Tighten the following fasteners:
Tighten the bolts to 13 inch lbs. (1.5 Nm)
Tighten the nuts to 89 inch lbs. (10 Nm).
Install the drain valve (3).
Connect the electrical connectors, as necessary.
Install the right rear wheelhouse.
Install the right rear quarter trim panel.
Add the engine coolant.
Inspect the system for leaks. If the fluid charging system is not used, the system must be burped to release air bubbles.
Heating, Ventilation, & Air Conditioning > Heater Core > Removal & Installation
Drain the engine cooling system into a clean container for reuse.
Remove or disconnect the following:
Negative battery cable
Heater hoses from the heater core
Temperature control cable from the heater case assembly
Disconnect the mode control cable from the heater case assembly
Instrument panel carrier to provide access to the heater case assembly
Electrical connectors that may interfere with the heater case assembly removal
Heater case assembly-to-chassis screws/nuts and the assembly. Place the heater case assembly on a bench.
Heater core cover screws
Heater core from the heater case
View of the heater case assembly-Sierra & Silverado
View of the heater core-Sierra & Silverado
Install or connect the following:
Heater core to the heater case
Heater core cover screws and tighten to 14 inch lbs. (1.6 Nm)
Heater case assembly and the assembly-to-chassis screws, then, tighten the screws to 35 inch lbs. (4 Nm) and the nuts to 80 inch lbs. (9 Nm)
Electrical connectors, as necessary
Instrument panel carrier
Mode control cable to the heater case assembly
Temperature control cable to the heater case assembly
Heater hoses to the heater core
Negative battery cable.
Refill the engine cooking system.
Run the engine to normal operating temperatures; then, check the climate control operation and check for leaks.
Heating, Ventilation, & Air Conditioning > Air Mix/Mode Actuator (Blend Door) > Removal & Installation
Remove the floor air outlet duct extension (1) from the floor duct (2).
Remove the floor air outlet duct extension (1) from the floor duct (2)
Disconnect the electrical connection at the blend door actuator (10).
Blend door actuator and related components
Remove the blend door actuator mounting screws from the HVAC module.
Remove the blend door actuator as an assembly with the actuator cam.
Remove the blend door actuator mounting screws from the HVAC module
Install the blend door actuator as an assembly with the actuator cam.
Line up the heater/defroster valve lever with the blend door actuator cam slot.
Line up the A/C valve lever with the blend door actuator cam
Install the blend door actuator mounting screw to the HVAC module.
Tighten the blend door actuator mounting screw to 14 inch lbs. (1.6 Nm).
Connect the electrical connection at the blend door actuator (10).
Install the floor air outlet duct extension (1) to the floor air duct (2).
Some good reviews for getting the smell out.
All kinds of diagrams here. I am about a little more than halfway down the page still looking. Any signs of where they may be getting in, like maybe leaves stuck in the hole?
Its going to be difficult for me to determine where they are getting in by looking at diagrams and guessing where they came in,but if you want diagrams of how things go together that is a good website for diagrams.
Thank you Heavy Chevy 396, you have given me a lot of diagrams and info to get started, I rate you A -1 on my scale. You gave me the info, I wish you could give me the skill, I hate all this plastic crap. It's so much easier on my 61 Galaxie Sunliner.
Thanks again for helping a Ford guy.