Whatever it is set to on your heater's control keypad.
Ultimately, it should be whatever temperature makes you comfortable, but I'd say a normal temperature would be around 65 degrees or so.
55 degrees above zero Fahrenheit
Depending on the year, make, model along with if it has single or dual a/c systems and what the outside temperature is, it can be between 36 to 48 degrees...... Simply, the A/C vents temperature should be whatever you set the thermostat as.
in the floor.
On the vents closest to the main unit it should read around the same temperature that the thermostat is set to after its been running and then as the venting increases the temperature should be less, between 2 to 10 degrees different depending on how well the ducting is in the attic........
Heating vents should be located near the floor since hot air rises. If the heating vents are located near the ceiling the heat would stay there and not warm the room.
on the floor on the floor
Turning the thermostat to a higher temperature does not make the air coming out of the vents hotter on a central AC with a heat coil. The temperature setting on the thermostat simply tells the system when to stop cooling or heating, but it doesn't affect the actual temperature of the air being produced. The heat coil or furnace is responsible for heating the air, not the thermostat setting.
There is probably a fuel leak somewhere. You should have a professional check it out ASAP. There is a possibility of a fire if left alone.
Heating vents should be placed on or near the floor because heat rises. In rising, it will warm the air of the room. If the heating vent were near the ceiling, the room would stay chilly, even though heat was being poured into it.
replace? why not fix it?
A thermostat for heating or a thermometer for air temperature is typically placed on an inside wall (not outside wall), and away from heating vents or direct sunlight.