Too Cool...Heater not functioning correctly

On my 1989 XJS v12, I am having an all too cool experience for winters here in Syracuse, New York. When I turn on the heat, it’s cool air, but…when I switch to defrost, warmer air, not hot, but warmer air flows only through the defroster areas. It’s seems backwards. How do I receive warm air through the correct channels?
Happy Thanksgiving.

Check the vents in the footwells. That should be hottest. Mine is lukewarm also.

Haven’t got around to checking, as Seattle ain’t that cold, but I’m assuming the heater core needs replacing?

If it’s clogged up. That’s perhaps the least likely scenario, though. Far more likely the flap controls aren’t working properly.

Dash vents pushing lukewarm air, footwells cold…not good.

Hi. Vents and dash vents pushing luke warm air when in defrost. When control turned to low/med/high…footwells and vents cold. This car was only driven 5-7 hundred miles per year for 11 years. I have noticed the car is limbering up in other areas.