Hey Scotty,

I uploaded a youtube video link where I am explaining the heater problem of my 2004 Highlander with 156k miles in NYC.

https://youtu.be/Ocwp4etL-qo

My trusted mechanic has changed waterpump, timing belt, coolant and thermostat recently (OEM parts).

Before these changes the AC was not working properly, now the AC works great.

Car runs great, heat also works but inconsistently. 

Temperature gauge is stable therefore no overheating / air in the system problem.

Both black hoses going from the engine into the dashboard are very warm, so no problem here either.

when I turn the heater on full blast and full heat, it heats up well for a few seconds, then drops to less warm before I slightly turn up or down the heater.

Any idea what is wrong?

Thanks in advance 🙂

Stan