Had a mechanic install heater core in 2002 dodge ram 1500, still have no heat. He tried blowing it out but didn't work. He said the motor needs blown out but He doesn't know the motor is only 5 years old. Any idea what to do.Do you think he blew more debris in heater core. Although the core only worked for 10 minutes. After he installed it.

Back flush the core. Common problems in a Ranger, not sure about your truck.