No Heat - heater not working?

Is the engine heating up quickly and running at a normal operating temp?

Joe

Hi:
When the engine first hits normal operating temp and the heater is still cool, feel both heater core hoses. They should both be hot. If they are, there seems to be a problem with the blend door. If one is hot and the other cool, flush the heater core.

Let me know what you find.

Joe

Make sure the coolant is full. Make sure the engine is running at a normal operating temp. Make sure the heater core hoses (both) are hot when the engine is hot, running, and the heater is on. Make sure the blend air door is working.

The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.

Hi:
Is the problem that the fan isn't working or the heater blows cool air?

Joe

Ok, I need you to check a couple things so I can identify where the problem.

First, with the engine running, hot, and the heater on hi, feel both heater core hoses. Both should be hot. LEt me know what you find.

Second, is the engine running at a normal operating temp (not too cold)?

Joe

Check heater core if its clogged-up if okay replace the thermostat and see what happens

I need you to check something. With the engine on, hot, and the heater on high, feel both heater core hoses and let me know if they are both hot.

Joe

Check to see if your heater control valve is getting vacuum. It's pointed out in pic. If not check for a vacuum leak starting at engine. If it gets vacuum with heat on then the valve is bad and needs replacing.

Feel the upper radiator hose when the engine is warmed up. It should be too hot to hold onto for very long. If it is not, suspect the thermostat. Dash gauges are notoriously inaccurate so you can't go by that to determine if the thermostat is opening at the right temperature. All dash gauges are good for is for YOU to notice when something is out-of-the-ordinary. To know the exact coolant temperature you need to connect a scanner to view live data and look at what the Engine Computer's temperature sensor is showing.

If the radiator hose is hot, feel the heater hoses. If they are not as hot, look for an inoperative water control valve or some other restriction in one of those hoses. A heater core shouldn't be corroded after 12 years unless the coolant wasn't replaced regularly. Was yours replaced because it was plugged? If so, there was likely some casting sand stuck in the engine block and more of that is breaking loose. That could cause a new heater core to become blocked, but most of the time that can be dislodged and cleaned out by running water from a garden hose through it.