No heat new thermostat fan blowing cold both

If both hoses are hot, the problem could be the inside...could be a blend door actuator

Most likely it is the heater control valve that shifts air from blowing across your heater core to your air conditioner core.

If your fan works and your car is fairly new..meaning your heater core isn't dirty and full of craap...then it is the climate cotrol valve.
If you are lucky, it might be a thermostat that is bad and blocking hot water from entering your heater core. Bottom line, if hot water doesn't circulate thru that little heater core, you won't get heat.
You might be able to look under the hood and grab the hot water lines that go thru the firewall and feed your heater core. If they feel cold to the touch after engine has warmed up, then you aren't getting circulating water to the heater core. If they feel nice and warm, then the heater core is fine, but your climate control valve has closed off the fan that blows across the core to disperse heat into the cabin

You heater core is probably clogged up with contaminates! If the water is not flowing through the core for the fan to blow the heat off the core you will not get heat!

thermostat is sticking open

Maybe your radiator is clogged.

Check the heater core by checking the hotness or coldness of the 2 tubes at the firewall that lead to the heater core.

If both tubes are hot, the heater core is fine. If both tubes are cold, then the heater core is plugged up and will have to be flushed out or replaced.

The thermostat, if stuck open, will delay the heating up of the heater core. It's not hard to replace the thermostat.

Thermostat Removal & Installation 4.2L Engine To Remove:

1. Before servicing the vehicle refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Some of the coolant
   • The upper radiator hose
     
     
   • The bolts (A).
   • The water outlet connection (B)
   • The water thermostat and paper gasket assembly (C)

To Install:
NOTE: The water thermostat is indexed and must be installed correctly.

1. Install or connect the following:
   • The water thermostat
   • The thermostat
   • The water outlet adapter
   • The bolts
     1. Torque to: 80 inch-lbs (9 Nm)
   • The upper radiator hose
   • The coolant

4.6L/5.4L Engines To Remove:

1. Before servicing the vehicle refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Some of the coolant
   • The upper radiator hose
     
     
   • The bolts (A)
   • The water outlet connection (B)
   • The water thermostat
   • The O-ring (discard)

To Install:

1. Install or connect the following:
   • A new O-ring to position the water thermostat in the upper intake manifold
   • The water outlet connection onto the upper intake manifold
   • The bolts
     1. Torque to: 18 ft-lbs (25 Nm)
   • The upper radiator hose
   • The coolant

you either have a closed thermostat or a blockage in the radiator

did you buy the heater cores new heater core and radiator is two different things sounds like you thermostat is bad touch your bottom hose and your top are they both hot if ones hot and ones cold water is not circulating bad thermostat is the heater core put in right

The heater core is possibly blocked or the temperature adjuster is not working.

First check the controls to be certain that the temperature aduster is working and the flaps/doors that direct the flow of hot air are working.

If they are..........

Check heater hose temp. If one is hot and one is cold, you are not getting flow through the heater core.

Bleed it to remove an air blockage.
If that does not work, flush the system.
If that does not work, replace the heater core.

Karl at topgunwon.com

have you checked the coolant level on the rediator?if its low you wont get alot of heat