No heater function

Check to see if the hose going out of the heater core is hot. If not, you have a plugged heater core.

IF you have hot coolant going through the heater core, then the blend door has to be the problem.

Hi,

It sounds like you have checked nearly everything. If the blend air doors are working, the coolant if full, and the engine is at normal operating temperature, the next thing I would suspect is the heater core is plugged.

Take a look through this link and see if it helps.:

https://www.2carpros.com/articles/car-heater-not-working

Do me a favor. Start the engine, turn the heater on high, and allow the engine to reach operating temperature. Next, feel both heater core hoses. Both should be hot. If they are, then the problem is in the vehicle (likely blend air door). 4

If only one is hot, then the core is likely plugged. Here is a link that shows in general how one is replaced:

https://www.2carpros.com/articles/replace-heater-core

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Here are the directions specific to your vehicle. The directions below correlate with the directions.

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2004 Honda Truck Odyssey V6-3.5L
Heater Unit/Core
Vehicle Heating and Air Conditioning Heater Core Case Service and Repair Procedures Heater Unit/Core
HEATER UNIT/CORE
Heater Unit/Core Replacement

SRS components are located in this area. Review the SRS component locations, precautions, and procedures in the SRS section before performing repairs or service.

1. Make sure you have the anti-theft code for the radio and the navigation system, then write down the frequencies for the radio's preset buttons.
2. Disconnect the negative cable from the battery.

pic 1

3. From under the hood, open the cable clamp (A), then disconnect the heater valve cable (B) from the heater valve arm (C). Turn the healer valve arm to the fully opened position as shown.
4. When the engine is cool, drain the engine coolant from the radiator.

pic 2

5. Slide the hose clamps (A) back, then disconnect the inlet heater hose (B) and the outlet heater hose (C) from the heater unit. Engine coolant will run out when the hoses are disconnected; drain it into a clean drip pan. Be sure not to let coolant spill on the electrical parts or the painted surfaces. If any coolant spills, rinse it off immediately.

pic 3

6. Remove the mounting nut from the heater unit. Take care not to damage or bend the fuel lines and the brake lines, etc.
7. Remove the dashboard.
8. Remove the evaporator.

pic 4

9. Remove the mounting bolts and the heater unit.

pic 5

10. Remove the self-tapping screws and the clamp (A), then carefully pull out the heater core (B) so you don't bend the inlet and outlet pipes.
11. Install the heater core in the reverse order of removal.
12. Install the heater unit in the reverse order of removal, and note these items:
- Do not interchange the inlet and outlet heater hoses, and install the hose clamps securely.
- Refill the cooling system with engine coolant.
- Adjust the heater valve cable.
- Make sure that there is no coolant leakage.
- Make sure that there is no air leakage.
- For evaporator and A/C-related information, refer to evaporator removal and installation.
- Do the PCM idle learn procedure.
- Do the power window control unit resetting procedure.
- Enter the anti-theft code for the radio and the navigation system, then enter the customer's radio station presets.

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Let me know if this helps or if you have other questions.

Take care,
Joe