Very Low Heat From Heater Core?

1993 Mazda MX-3 Base 1.6

Recently I've come across the problem of having very little heat through the heater core. While the blower is not running, the heater core hoses are both hot, while the blower running the inlet hose is hot while the outlet is cooler. Which means that the heater core is not clogged. The upper radiator hose is hot, while the lower cool which I would expect. The thermostat has recently been changed along with the cooling system being burped properly, including the blower being on high/hot while burping the system to get rid of any possible air bubbles within the heater core.

I noticed while changing out the thermostat that the coolant temperature sensor was eroding because of the glycol mix of the antifreeze. It will be replaced. However, I haven't noticed that the fans turn on because of this, but the coolant gauge reads normal operating temperature whether idling, cruising at low RPM, or doing 65 MPH down the freeway. The water pump works fine as I can visually see the coolant flow from the water neck on the radiator.

I would imagine that the radiator cap would cause a problem much like a clogged radiator; opening sooner rather than later by the pressure in the system. As I'm not sure when the radiator cap was last changed, this is also a common problem when concerning loss of coolant (which isn't a problem immediately). The other problem that I would see is the coolant temperature sensor itself, however, it has nothing to do with the heater core temperature, rather the fans not turning on. While squeezing all the hoses (upper and lower radiator, heater core hoses), when cold and hot, the coolant raises in height with the radiator cap off. This might lead me to believe that there might be a sleight blockage in the system not allowing the hot coolant to flow through the heater core effectively.