1966 poor heating

[Al63]

Hi,

Heating is poor in my 66.
I replaced the water valve 5 years ago and I tested it last week. It seems okay.
I have 8 to 17 inches of mercury vacuum on the line connected to it (depending on the position of the Hi/Lo selector lever).
The heater hoses going to and from the heater core are hot
The blower motor is okay
the blower door operates normally.
But despite all that, the air blown into the car is tepid.

Any idea?

Thanks

 

[My1966T-Bird]

Have you checked your vacuum control system for any leaks or disconnected hoses? The heater/ac switch operates off of the vacuum control system.

 

[Al63]

Have you checked your vacuum control system for any leaks or disconnected hoses? The heater/ac switch operates off of the vacuum control system.

I am not sure to understand what you mean by "The heater/ac switch operates off of the vacuum control system".
Where are this/these switch(es)?
Are they connected to a vacuum line?
Thanks

 

[74 Harley]

Pull the blower motor out and make sure your heater core is clean. Many a mouse has built a nest in a heater box blocking airflow.

 

[My1966T-Bird]

I am not sure to understand what you mean by "The heater/ac switch operates off of the vacuum control system".
Where are this/these switch(es)?
Are they connected to a vacuum line?
Thanks

The switches that you operate on the dash connect to the vacuum control system under the dash.

 

[Ward 57]

The switches that you operate on the dash connect to the vacuum control system under the dash.

His heater hoses are hot but is there a valve at the heater core that is not functioning? Don't know the system but everything else seems to be working.

 

[74 Harley]

If both heater hoses are hot then the valve is open.

 

[Ward 57]

If both heater hoses are hot then the valve is open.

Clogged heater core? My first thought was the dampers in the plenum but he said they worked.

 

[Al63]

Thank you all for your thoughts.
I will check the heater core cleanliness.
However I wonder how the ventilation works. The blower motor sucks the air through the heater core. But where the fresh air is coming from? Is there a door upstream the heater core? Could it be closed or blocked?