My girl has a 2000 Dodge Intrepid and when she turns the heat on it blows cool air. l had a buddy of mine who works on cars look at it and he thought the heater coil might be clogged so he pulled the hoses and blew air thru but it did not work then he tried to see if the hot/cold switch behind the dash was working properly and turns out it was. He said that the car is hot underneath the hood but the air is cool when it comes out the vents. He ruled out the thermostat because the car is not running hot or anything. What else could be causing this?

the heater core has gone out

Well it is an American car, maybe that is why. Trying going with some good cars for now on. Usually European or Japanese make are really good.

Bring it to an auto shop to get it checked. But since it is only 8ish years old you might still have the warranty. Give the dealer you got it from a call to see if you can bring it there for repair.

Replace the thermostat, it heats the water, listen to me.

l just asked this an hour ago. Some of my were clogged or broke heater core, not enough anti-freeze, coolant system needs flushed.. if u get anything better, let me know.

the thermostat could be stuck in the open position & that would make it run cooler all the time,one does not have to be stuck closed to be bad,id consider changing it ,that will prevent it from heating up enough to give off any heat,and it makes the engine run cooler but does not allow it to heat up enough for heating purposes,id also check the blend doors on it & see if they was opening like they should be & feel the heater hoses to see if they r even getting hot,that will be a dead give away of a bad thermostat,good luck on it,

Chrysler 2.7 & 3.5 Liter engines have a little problem when it comes to heat. If u get an air pocket in them (from a leak that may be small but still there) u will not get heat from the heater. The vehicle will not overheat as the heater is almost the highest point in the system so coolant is still flowing through the block & radiator. If u look to the top & front of the engine on either model u will find there is a 10mm bleeder screw on there. Fill the engine all the way with coolant into the reservoir & warm it up. As the engine is at operating temp open the bleeder until only a good stream of coolant with no air comes out. Also when filling the system u will see on the fill neck the overflow hose. This goes to the cooling system overflow reservoir. Take this hose off at the filler neck. Using a funnel that fits into this hose fill the coolant back into the reservoir till u see it about halfway up the tank. You will notice this on the side of the tank that is next to the drivers side fender well. By also filling this overflow reservoir u will make it so that the vehicle will no longer be able to bring in air to make the air pocket. But u need to have the system pressure tested to find where the coolant leak is & have that fixed also or u will be in the same spot again.

l have a 99 pontiac that does the same thing every time its low on coolant. Just add some should be good