TOYOTA PICKUP HEATER

The Air Is Blowing Normal However It Is Not Hot. We Have Flushed All The Fluids, Changed The Thermostat And Also Checked That The Lever...

It Has 2h Diesel Engine But Priviously It Was Petrol 1hz Engine. Now When I Drive It, The Whole Cabin Will Heat Too Much, Till I Sweat....

My Truck Runs Fine Until I Turn The Heat On In The Cab Then The Engine Temperature Goes Up. What Causes This