We just bought a 2005 Mazda 6 for my daughter.
The heat is barely warm, even after 45 minutes of driving. The temp gauge is just a little bit past "C", when we stop the car, the gauge does go towards half way, but the heat is still lukewarm.
Any suggestions??
Thanks
Barry

 

Remove the thermostat, carry out a full cooling system flush, refit the thermostat, fill the system with a 50/50 coolant mix, bleed the system & go from there.

 

a few things to check.... first make sure there are NO KINKS on heater hoses /
Coolant is at right level
Heater hose outlet from water pump to heater hose is not blocked or cracked

worse case.... heater element is in need of replacing
good luck any questions reach out