heater not blowing hot air on ford explorer?

Drain the coolant from your Explorer into an adequate container by opening the drain plug at the bottom of the radiator. Save the coolant for reuse if it is relatively new and clean.

Remove the negative battery cable from the battery.

Follow the upper radiator hose to the front driver's side of the intake manifold, where it meets the engine. This is where the thermostat housing on your Ford Explorer is located. If necessary, remove the air cleaner duct for easy access to the housing.

Loosen the clip on the end of the radiator hose and pull the hose off the thermostat housing. Use a 10mm wrench or socket to remove the two retaining bolts on the thermostat housing cover. Remove the cover.

Note the position of the thermostat before removal. Pull out the old thermostat. Seat the new thermostat inside the housing in the same position as the old one, spring-side facing into the engine. Install new gasket over the thermostat.

Reattach the thermostat housing cover and the radiator hose. Reinstall the air cleaner duct if removed earlier. Fill the radiator with reserve or new coolant. Start your Explorer and run with the heater blowing until the engine gets warm. Check for leaks.

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Had same problem on 2002 Ford Explorer: Heater blowing cold air. Seemed like symptom of one of three likely problems: 1) Radiator fluid low 2) Thermostat needed replacing 3) Flushing of cooling system, incl. heater core. 1) Radiator reservoir was low, but added coolant (look to make sure you're adding the right color; green or yellow), that failed to fix it 2) Thermostat appeared to be working (felt hoses that are beyond the thermostat and they were letting hot fluid through) 3) The two lines leading into the heater core; one was hot, the other cold (an inlet to the heater core and an outlet from the heater core). Seemed to indicate a blockage somewhere in the heater core. Took it to a reputable shop and asked for a radiator flush. I did not realize a "radiator flush" was a low pressure process that essentially replaces your radiator fluid at a slow pace. I previously saw another posting that required the force of a garden hose to free the blocked heater core of debris. I asked if this could be done. They hooked up to the inlet and ran the water through and tested; no heat. Tried hooking the outlet line and tested; WORKED! Whatever was blocking the flow of radiator fluid was now removed and the heater works fine. They said the maintenance recommendation for this vehicle is to have the radiator flushed every 30,000 miles. I guess after this point the radiator fluid starts to accumulate sediment and other debris that can clog smaller areas of the circulation system, such as within the heater core.

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. It has heater hoses that run hot water straight into the heater core on the back of the engine on the passenger side. It is important to understand how the heater works in your car before you can begin to try to diagnose why it is not working. The part that transfers heat into the passenger compartment is called a heater core. A heater core can be thought of as a miniature radiator. The car engine's coolant flows through the heater core while the fan (also called a blower), blows air through the heater core fins. When air blows through the heater core fins, it is warmed.------------ Now for troubleshooting:----

Start by checking the coolant. As we already said coolant is what warms the heater core. So if the coolant is low, there may not be a sufficient amount of warmth to transfer heat to the air in the passenger compartment.Once the coolant is full, feel the heater hoses that go through the firewall. With the engine at normal operating temperature, BOTH of the heater hoses should be hot to the touch. If only one is hot, this indicates there is is a blockage in the heater core or there is air trapped in the heater core.One hose hot, one cold, points to a plugged heater core.If this is the case,try flushing the heater core.There are no valves in the heater core; it is free flow at all times.Also check the head gasket. just because there is no water coming out of the exhaust dos,nt mean the head gasket is ok.How much pressure is in the system?.Are the water hoses very hard when the engine is hot?.......air in the system will stop the heater from working.------------Also try this procedure to clean the block in the heater core.If there is any:--- Put in a cleaner, Prestone, and drive car few hours.Then check if nNo success. Then get cleaner made by Gunk.You can get it from any local auto part store. Drain heater core, leave both heater hoses attached to the heater. Remove other ends of both hoses from the tubes on the thermostat housing and raise these ends above the heater core. Pour Gunk cleaner in one hose and add water until cleaner started to come out other hose. Leave this sit 4 hours and back flush heater core in both directions. Next back-flush block and radiator in both directions. Water should come out of tube on the thermostat housing that has a hose attached to the outlet of the heater core.If not coming then Flush water directly into this tube about 15 to 20 times and you will hear a thud of water coming out.. Back flush block and radiator again and this time water should out the tube previously blocked. But if problem is same and no difference.Then is faulty heater core.Its causing the problem and it needs to be replaced.Also check the radiator,if its blocked then get the radiator back flushed too..