Engine heats as normal both heater hoses hot at firewall heater blower works but no heat

are the small hoses to the firewall heating up? ck the heater control valve

Without more specs re: engine size etc, I'd have to say look close at firewall between engine and cab for hoses /tubing going into passenger compartment through firewall.

Make sure the heater hose is hot with the engine is warm. The heater hose goes into the firewall and into a heat exchanger/ blower fan that will give you defrost and car heat. If the heater hose doesn't get hot you may have a blockage in the hose or at the radiator outlet.

Does the blower motor still work?
Lift the hood after the engine is at normal operating temperature, and feel the two heater hoses going from the engine into the firewall. Both should be hot if the coolant is circulating through the heater core. If they are, one of the inner doors in the heater box may not be operating. The doors are either cable operated or vacuum operated from your heater controls. One door in the box should be open when heat is desired to let the blower fan blow air across the heater core, and then to the vents where heat comes out. The heater box is usually rather large, under the middle of the dash. Have someone check your temperature blend door- I believe that is the one that may be at fault.
Now if only one of the heater hoses is hot, and the other is cool, the coolant is not circulating through the core. Look for an in-line water valve on one of the hoses. These also may be cable or vacuum operated from the heater control head. Not all vehicles have a valve, just some do.

It's just a simple small radiator. Coolant circulates through it, and the cores' fins give off heat that is picked up by the blower motor.
When the engine is at normal operating temperature, feel the two heater hoses. Both should be hot, verifying coolant is circulating through it. If only one is hot, the core may be plugged or have an air block. You can take off the core outlet hose and observe stream flow when engine is running and heater on high heat-flow should be slow but steady. The outlet hose will run from the firewall to the front of the engine into a fitting near the water pump. Some cars have a water valve in one of the hoses-make sure it is open, for coolant to circulate.

The core may be plugged, or it may have an air lock, or the core may be fine and the doors in the heater case may not be opening properly to pass heat.

With the engine at normal operating temperature, feel both the inlet and outlet core hoses at the firewall. If the coolant is circulating both hoses should be hot. If only one is hot, try cracking open the outlet line, with engine running, to get flow started from an air block. (The outlet line will run from the firewall to the front of engine near or at the water pump housing. The inlet for the heater comes off the top of engine from a head fitting and goes to the firewall.) If no flow results, the core may be plugged. To flush the core, take both hoses off at the firewall or off at where they fit on the engine, and put a garden hose into the outlet-flush it backwards-run until clear-let the water run to ground or use a catch can if able to. Some people use compressed air into the core instead of water flushing. Either way, you should see some sediment come out if it had any blockage. Once you get the heater core circulating, any further heater problems need to be addressed at the heater case. Make sure the temperature blend door can open and close-this door opens to let blower fan air pass across the heater core.
Good luck.

have 2002 altima,blower works no heat at idle and very little heat when accelerating.I changed carbon cabin filter,made sure little gear under dash to temp knob wasnt broken,flushed and bled system.Nothing worked so checked hoses to heater core and found inlet hose was hot,outlet hose was not.So investigated this problem and came to conclusion heater core was clogged.An easy way to check is to get car to normal running temp. put on heater and blowers at full.Go under dash on passenger side where counsel meets firewall,this is where heater core core inlet and outlet aluminum tubbing go through firewall,you will be able to feel both tubes one closest to you is outlet, so if this one is not hot and and other is your heater core is clogged.I detached both inlet and outlet hoses to heater core from water control valve.Then I blasted water with waterhose and nozzle set at jet,first through outlet hose to blow gunk out,then through inlet hose until water runs clear.Reatach hoses fill and bled system.heater works great nice and hot!

Check to see if the heater core hoses going into the firewall are hot when the engine radiator hoses are hot. If one heater core hose is hot and other is cool, then the heater core is blocked/plugged. If they are both cold then the hoses are blocked. Trace them both back to the engine and make sure there is no on/off valve on the intake to turn on. Some of those valves are vacuum operated or electrical. Just depends. For a quick fix. You can remove that valve and install a screw in fitting to the intake manifold that has a barb on the end to slip a hose over. But the heat will always be on hot.

Hello

I recently had a simular problem...try to follow the heater hoses that come from the engine and go into the firewall to the heater core... one of the 2 hoses connects to a plastic valve right before the firewall. This valve shuts off the flow of hot coolant into the heater core when heat is not needed.. Look carefully at this plastic valve, there is a wire pull cable with a small loop at the end that connects to a lever on the valve. Have a helper work the heat controls and make sure the cable pulls on the lever at the firewall valve...I've seen some cables disconnected. Hope this helps with your diagnosis.

Under the hood on the pass. side firewall are two heater hose lines. Start the car and let it get at normal operating temp. One of the hoses is the "in" to the heater core, if you touch it it should be hot. The other hose is the "out" of the heater core, this hose should be warm and not really hot like the "in" hose. If the hose going in is hot and the other cold, then your heater core is clogged. There is a valve connected inline with one of the heater hoses, this is the heater control vavle.
If the valve does not open, you will not have any heat either.