Hello and welcome. I think that is the key to your problem-'190deg going in and out.'
If there were a problem with the temp door in the dash, then no airflow would go over the heater core to cool it. Usually you can hear a change in the airflow when swiotching from cold to hot, or hear the door move. If you confirm the door moves, then once again back to 190 deg in and out.
If the heater core is plugged, then no coolant will flow through it, and the coolant temp on the outlet side would be as hot as system coolant temp justt for the fact it is a hot engine, and all coolant would be the same temp. the heater core is just like a radiator, hot coolant goes in, gets cooled by the airflow over it, then come out the other side not as hot- as long as coolant is flowing.
Auto technician
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