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well recently it has been warm but tonight it started to get cold again so i went to turn on my heat and to my surprise all that came out was cold air. The car was warmed up and I had been driving for some time. What troubleshooting steps could I do to find the problem before i have to take it to the shop. Thanks

 
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its usually your t-stat 9 out of 10 times

 
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Is it hard to test the thermostat yourself?
I know its not that hard to take out, but what about testing it?

 
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you dont need to test it, if the car is getting warm and the car has coolant in it, then it means your t-stat is not opening up

 
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Well I put in a new t-stat because the lower rad hose wasn't warming up at all so I figured I put in a new one. I still dont have any heat tough the lower rad hose gets hot now. I checked every hose that I could see that would have coolant running through it and they all get hot after the car is warmed up. Would this mean my heater core is shot and how could I determine this for sure. Thanks

 
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either radiator or heater core, check under your floormats on the inside fronts for any coolant, if there is, its your core for sure