Is there a directional flow for the water through the heater core, or can either hose go on either nipple? When temp is put to heat, it only blows warm air, never gets really hot air. Thermostat appears to be working as the temp gauge sits right where it should be. Winter is on the way, and this year I'd really like to have some hot air.

 

You probably have a bad blend door actuator that is only partially opening not allowing the full heat to pass through. This is less likely but you could also have a partially clogged heater core. With the engine at full temp see if both heater hoses are at the same temp. If they are then it is the blend door actuator. If one is hotter than the other then it is the heater core.

 

Both hoses are the same. I've flushed the core a couple of times and water runs freely from both sides. Where is the blend door actuator located? Also, when you push the button for fresh or recirculated air, there is no change. Is that the same problem?

 

The blend door actuator is behind the dash. My 99 had 3 different actuators. I believe the other problem could be a different actuator. Check out Youtube, they have videos on how to change them.

 

The issue with your fresh air and recirculation air is a different ventilation door problem. That damper/door is located above the heater box, under the passenger side dash above the glove box. Probably the door actuator needs replaced. Again look on youtube for vids. See attached drawing.

 

Attached file won't open correctly, but will check on youtube. Thanks for the help.

 

Try this...