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Q: NO HEAT! on 1994 Chevrolet Camaro

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My 94 camaro has no heat. Engine is getting up to temp.The radiator and heater coil has been backflushed. temp gage is new- still no heat. Anti-freeze level is good.
How does the car get the "signal" to open valve to let water into the heater? Could this be bad? how can I tell?
No car image 94a1663db56199c5353592009e34aaa51078a2469bed068bb8d6f0ba43accf97
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The water valve is vacuum operated and the vacuum signal is sent from the dash control panel. You will need to check the heater hoses to see if a valve is installed in one of the hoses. You can also try warming the engine and then feel the heater hoses coming in and out of the heater core. with the heater on, BOTH hoses should be warm. If both hoses are warm that means the coolant flow through the heater core is OK and the fault is with the temperature control inside. The temperature blend door is controlled by a cable connected to the temperature knob on the dash. Make sure the temperature blend door is moving in relation the the knob. If you move the knob and the cable does not move you will need to find out why. If one heater hose is warm and the other is not that means coolant is NOT flowing through the heater core. The core may be plugged and backflushing did not correct the problem or the valve is not working. Check for vacuum to the valve. Vacuum should come and go as the temp control is moved from hot to cold. If everything checks out OK there is a service bulletin from GM stating that the heater core seal may be out of place inside the heater box causing cold air to bypass the heater core. The complete heater box must be removed to repair this fault so make SURE everything else is working correctly before you try and repair the loose seal.
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