Here are some images I marked up to show the flow.

Like PAhonda is saying you need to check whether the outlet hose gets hot.

The heater unit door should also move depending on whether you select heat, cool, etc.

 

Now I am a little confused after redbull's comment.

I did not think there is heater door as illustrated in your first picture in the above post?

I thought the heat OR no heat was only controlled by amount of the hot coolant let into the heater core by the tap that is controlled by the temp ****.

Air flows over the heater core irrespective of heat is selected or not, am I right?

Also now I am curious where is the Evaporator core in the HVAC unit?

(The one beside the airfilter seems to be the heater core)

 

The closest component to the air filter is the evaporator (cold radiator for a/c).

The heater core is more in the middle of the dash. My 95 has a door like redbull stated. When you turn the heat to cold, the valve in the engine bay gets shut off and the door covers the heater core. I am guessing that you 2000 is setup the same way, but I can't be certain. Not sure why this is done, but there has to be a reason.

Does the hose between the valve and the engine bay firewall get hot when you turn the heater to hot? Does the outlet temperature remain cool? If so, I think you have a clogged heater core.

 

I believe all the Hondas' heater unit had door(s), they were just positioned differently on later Accords. I marked some of the images up to give a visual too. #5 is the mode control motor, #6 is the air mix control motor.

Some info.:
Air Delivery: The heater control panel controls the blower motor and supplies a reference voltage to the air mixture control motor. The air mix and mode control motors each receive inputs from the control panel. The air mix motor regulates the mixture of cold and hot air by varying the position of the heater door. The mode control motor controls the direction and volume of outlet air. Use the mode control buttons to select the vents the air flows from. Some air will flow from the dashboard corner vents in all modes.

If you select a hot temperature setting, the heater door directs air flow through heater core. A cool temperature setting blocks the air flow through heater core. Incorrect door position can cause low heat air flow.

 

HI folks, need some quick small suggestion here,
I recently had my thermostat replaced as it got busted but this still did not solve the heat issue. And the mechanic suggested that the valve isnt opening properly.
So what I plan to do tomorrow is to remove the value and repalce it with pass through to ensure it is the valve indeed that is creating the problem.

The plan is to pinch the hose at the two ends of the heater valve and then remove it. Do you think this will create a air pocket in the system? Is this a self bleeding system or does it need some kind of bleed valve to be opened etc? I am assuming I would not loose a lot of coolant in the process though..

Also what is the safest Antifreeze coolant in this condition as I dont know if the system has a Dex Cool or no and I have heard that DexCool does not gel well with other coolants?

Thanks for all your help..

 

Did you reuse the old coolant when you replaced the thermostat? Did you use a Honda thermostat, because most techs on here recommend them.

I am not very familiar with the V6 setup. If there is an air bleed valve on the thermostat housing, then I would open that up to allow air to escape. You may just have to run the engine with the radiator cap remove to purge air from the system.

Not sure what coolant is in your system. All of the information should be in the owners manual. It may also have the procedure on how to properly change the coolant.

 

I did not do the thermostat replacement.. Got it done by a mechanic cos I got stranded on road (for $300)
So I dont know the coolant in the system.
So what do I do in such a situation?

Thanks I read the Manual now and V6 apparantly does not have a bleed valve. All I need to do it let it self bleed, run/check/fill/run/check/fill 3 times

 

Thanks everyone here!
I fixed it finally, it was clogged heater core!!

I back flushed it and now it works like magic! Ton of thanks..

This is my first mechanical work on my car!! thanks a ton!