Heater not working properly

You should be feeling heat in the vehicle. However, I'm surprised the temp dropped that much. Are you getting any heat in the vehicle?

Something has come apart. If you have full air flow and control over the mode door, something isn't allowing the heat to enter. There is only one heater core. If you have heat on one and not the others, it's not a core issue. You have replaced the air temp actuator. I have one more suggestion. Try this self diagnostic test and see if any codes show up.

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2008 Honda Accord V6-3.5L
Heating/Air Conditioning
Vehicle Heating and Air Conditioning Testing and Inspection Reading and Clearing Diagnostic Trouble Codes Heating/Air Conditioning
HEATING/AIR CONDITIONING
General Troubleshooting Information

How to Use the Self-diagnostic Function

The HVAC control unit has a self-diagnostic function for heating, ventilation, and air conditioning system. To run the self-diagnostic function, do the following:

1. Turn the ignition switch to LOCK (0) and then to ON (II).
2. Set the FAN CONTROL dial to OFF, the TEMPERATURE CONTROL dial on Max Cool, and select the VENT mode.
3. Turn the ignition switch to LOCK (0) and then to ON (II).
4. Press and hold the RECIRCULATION CONTROL button, then within 10 seconds press and release the REAR WINDOW DEFOGGER/MIRROR DEFOGGER button five times. Release the RECIRCULATION CONTROL button; the recirculation indicator blinks two times, then the self-diagnostic begins.

NOTE:
- The blower motor will run at various speeds when in the self-diagnostic mode.
- If there is any problem in the system after the self-diagnostic function is finished, the recirculation indicator blinks Diagnostic Trouble Code (DTC) 1 through 15. In the case of multiple problems, the recirculation indicator blinks in order with the lowest number DTC repeatedly.
- If no DTCs are found, the indicator does not blink.

Pic 1

1 - 15

pic 2

Clear the DTCs

When the problem is repaired, DTCs will automatically clear.

Max Cool Position Function

When the mode control button is in the MAX A/C position, the HVAC control unit will automatically select the recirculation mode and turn the A/C on. If the recirculation switch is pressed when in MAX A/C, MAX A/C turns off. If A/C is pressed when in MAX A/C, the A/C turns off.
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Let me know what you find
Joe

Once the engine reaches operating temp and there are no air locks, that should be all that's needed. I never heard of driving 8 to 9 hours to check the heater core or to make it operate.

If I recall, when you flushed it, the water flowed freely in both directions. If that is correct, that isn't any indication of a heater core issue. Are both heater core hoses getting hot now?

Let me know.
Joe

Hi,

That's a little cooler than I would expect at operating temperature, but you should be getting heat. I have a feeling this is a blend door actuator issue.

Hi,

Check the heater hoses with the engine at operating temp and the heater on.

Let me know.

Joe

If you had 92 degrees at one point, something is going on in the HVAC box. I want to say mode actuator, but at this point, I would have to remove the assembly and check to see if something is broken, disconnected, not getting power and so on.

Take a look at the pic I attached. It shows both actuators that have been in question. One is the mode door actuator which directs air flow direction. The other is the air temp actuator. At this point, I hate to ask again, but is the manual HVAC or automatic?

If you had 93 degrees at one point, the heater core isn't plugged. You wouldn't be getting heat if it was. Interestingly, if you had them replace the heater core, they would have to remove the HVAC box.

Let me know if you have confirmed both of these actuators are working.

Joe

Hi,

Automatic VS Manual is simple. With an automatic system, you pick a temp and the system maintains that temp. With a manual, the air temp coming into the vehicle is controlled by the driver via the blend air door.

I attached a pic showing both actuators.

Joe

If I can tell, it looks like the one button indicates auto, which would be the automatic climate control.

You know, a thought just came into my mind. If I remember (and bear with me. It's 2:11am here) there was an issue with a sand like material in the engine block cooling system from when these were new. I wonder it that is blocking parts of the heater core and hasn't come out when you flushed it.

It's just a thought. I'm a bit tired at this point. LOL

Joe

I totally understand. I can't tell you how many times it felt like I was standing on my head to access actuators. Not only are the hidden, but also there is usually hardly any room to work on them. I miss the old mechanical cables. They were much easier to deal with.