2003 silverado. no heat in cabin. water hose to heater core is hot on one side only. is there a valve before it goes to heater core oe is heater core plugged?

Question edited for clarity and typo, and add maker.
Question moved to model category.

The AC evaporator core and the heating core are normally two separate items. It is unlikely that the heater core is completely clogged. There must be a valve in your flushing circuit.

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• Insufficient, erratic, or no heat

• Low engine coolant level.
• Engine overheating.
• Plugged or partially plugged heater core (18476).
• Temperature blend door binding/stuck.
• Temperature blend door actuator (19E616).
• Incorrect heater control valve (18495) operation.

• Go To Pinpoint Test I .

Are the heater hose's going through the fire wall hot ?
I2 CHECK FOR HOT WATER TO THE HEATER CORE INLET HOSE WARNING: The heater core inlet hose will become too hot to handle and may cause serious burns if the system is working correctly. Allow the engine to reach normal operating temperature. Feel the heater core inlet hose.

• Is the heater core inlet hose too hot to handle?

Yes GO to I4 .

No REFER to Section 303-03 to check cooling system function.

don't know this van specifically, but some things to check, make sure cabin filter is replaced or clean, you didn't say if the blower itself works, if not, correct or replace. Check the hoses going to the heater core, if hot water is flowing thru the core, both hoses should be hot. Check the heater controls to make sure doors in the system are opening closing as they should, you may just be drawing in cold air and not going thru the heater core.

Some early cars have what is referred to as a hot water valve under the hood . It is hooked in one of the heater hoses , the supply side . The other hose is the return side , once the hot coolant goes through the heater core it goes back to the engine to get heated up again. This hot water valve is operated by engine vacuum. If you look at the fire wall or bulkhead , you should see two hoses going into the inside of the vehicle. those are the heater hoses. look for the valve on one of them. If you vehicle doesn't have one of this valves , you possibly have a mode or blend door problem . Does you car have Electronic Automatic Temperature Control or manual A/C-heater system ? The heater blower does work , all speeds ?

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!

The cooling system should be flushed but lets start with the heat,remove both hoses from the heater core, install hose to each end of the core about 3 ft long next take waterhose and and start to flush out start with one side and flush with hose on full water, then move to other side , do this a few times, water flow should be clean and flow good, after that if the heat is still warm replace the thermostat and that should solve the problem. good day.

once engine is hot
all cabin setting set to heat
check hoses going into cabin from engine - are they hot if not check - engine thermostat.
flush cabin heater core with water from garden hose - through both core hoses one direction then the other - to clean out core.
check vacuum doors in heater core box in passenger compartment.

if the engine is hot and no heat to cabin then heater core or shut valve is plugged feel the hoses going to the heater at firewall if one hose is hot then coolant isnt flowing to heater if both are hot then problem with vent flaps are not openeing heat door to allow air to flow over the core try that first

Possibly the heater core is 90% blocked. open enough to draw hot water in, (hose feels hot) but not enough volume to provide heat from very cold air, 10% hot water gets cold quick, coming from core..
Flush heater core in reverse direction - cold side in hot side out..

Just a theory..

Start with the engine hot and the temperature selector in the cabin set to max heat and the blower on. Raise the hood and locate the hoses going into the heater core (through the firewall). Check if both hoses are hot to the touch. If not, locate the control valve in one of the heater hoses and feel if it is hot on one side of the valve.

Have an assistant move the temperature selector inside the cabin. Watch the valve in the heater hose to see if it moves. If not, look for the problem with the mechanism. If it does, replace the thermostat.