1995 f350 blows cold air, heater core is hot but the air is cold

thermostat is sticking open

If the heater hoses are getting hot, the problem may be a faulty blend door under the dash. The blend doors direct air thru the heater core and the vents.

The only thing I can think of for this is maybe the "heat/cold" "diverter" is stuck!

Your heater core could be plugged with dust if this problem came up slowly I would suspect that. Another thing that cold be wrong is a trap door is not opening these are operated by cables vacuum or stepper motors. Confirm that something happens when you move from cold to hot on the control.

first feel the heater core hoses see if both are hot if so then your problem is in the blend air door must be stuck on cold. is your blower motor blowing cold air if not your blower motor might be the problem. the blend air door is down by the blower motor.

Find the two heater hoses going through the firewall to the heater core both need to be hot at operating temp. If both are hot the problem will be inside with the heater control. I only one heater hose is hot the
problem will be the heater core. I am assuming you have bled all the air out of the cooling system.

Sounds like there may be an air pocket in the system.
Try 'burping' the system. If this still doesn't fix the problem, check the temperature of the heater core hoses (in and out) The inlet should be fairly cool, the other should be piping hot. If they're both cold; the heater core has an internal blockage.

Next, replace the thermostat with a winter (180-195 F) derivative.
Bleed the system accordingly, and keep me posted!

my 2004 pontaic bonneville the heater hoses going into and out from the heater core are hot , but the heater blow cold air. ,

The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.

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maybe a blockage or thermostat is in backwards