[Bob Matthews]

The first thing I'd check is the heater valve - it allows the user to set the interior temperature and is controlled from the dashboard - maybe it's not opening and closing properly?

 

[Bob Matthews]

Bob,

I checked the heat (cold to hot) control on the dash and is moving the flap in front of the heater core.

Thanks

The flap cuts the air coming in, not the amount of water flowing through the heat exchanger, that's controlled by a valve!