Heater problems

[Starbaker19]

I’ve got an 05 Cummins with 226k on it. The heater barely works when the fan is low. I’ve replaced the thermostat and I’m not leaking coolant. I’ve flushed the heater core. My next step is changing the water pump. Anyone else have similar problems?

 

[jws123]

Your in the 4th gen section however being a 05 its probably due for a heater core or blend doors/actuators also make sure you got the air out of the system.