My Car Heater is Not Hot

heater not hotI have a problem with heat in my Chevrolet Astro Van. The air conditioner blower works fine and the antifreeze is full and the thermostat seems to operate and runs at about 170 degrees, but the heater is not hot enough inside the vehicle. I need help badly as I live in Minnesota and high today is 5 degrees.

Thank you,


Hey Steve,

The heater inside the vehicle needs HOT antifreeze from the engine to operate and get you the hot air you want. Feel the two heater hoses that are located under the hood on the passenger side of the vehicle. They should both be hot to the touch when the engine is at normal operating temperature (which is about 210 degrees F) .

If both heater hoses are hot, you probably have a control issue inside the dash or the dash selector switch, since HOT antifreeze is circulating inside the heater core located in the dashboard towards the passenger side.

If only one heater hose is hot, you might have a heater valve problem which is stopping the flow of hot antifreeze or the heater core is stopped up with rust and needs to be back flushed.

Below in the image you can see a flush kit that has been installed to one of the heater hoses.

flushing the heater core

Rust can build up inside the heater core (which is basically a small radiator) and restrict the flow of hot coolant. Just like a blocked artery in your body will restrict the flow of blood. You can buy a flush kit from your local parts house and hook it up to a garden hose and add a chemical that will help break down the rust.

Now, if the heater core is full of rust, the bottom of your radiator will be too, and you really can not flush that out, you will need to replace the radiator to get proper coolant circulation again.

More about heater core flushing in this video

If both heater hoses are NOT hot, you might have either a thermostat problem or a restriction in the radiator that is restricting the flow of hot antifreeze throughout the system.

Being low on coolant can be an issue too, since there is not enough hot coolant to circulate inside the engine and you might have a coolant leak somewhere that needs to be found and repaired. You should not have to constantly add coolant to the radiator on any vehicle.

Since you mentioned engine temperature at 170, I would suspect you have a lazy thermostat or the wrong type of thermostat installed. You need a 195 degree F thermostat for this vehicle….as with just about all other gasoline vehicles.

If both the heater hoses are not hot I would first replace the thermostat and see if that helps since its a quick and cheap repair and a good guess.

Please share this with your friends,
Austin Davis

Posted in: A/C and Heating

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