Heater stopped working

[TRDpro4R]

Hey guys, I have found several threads via search but I have yet to identify a solution.

2004 Runner V6 2wd with 196k miles.

Heater stopped working
Vents blow a lot of air, just not hot
Engine temp is perfect
Coolant system has been flushed and has new coolant
Thermostat has been replaced
Both inlet and outlet lines are warm to touch (the ones going through firewall)

I had a local mechanic flush the system and it blew heat briefly afterwards, then stopped. As in like 30 minutes of flushing the system, it blew heat then stopped.

Any ideas on why this would happen or what I should be looking at?

 

[TRDpro4R]

I’m wanting to check the actuator to make sure that is working. We were hearing a weird buzzing noise under the dash for awhile. I’m wondering that went out?

Does anyone have any info on how to check that?