no heater operation ?

Open up the radiator cap and start it up-pinch the upper hose for a few secs and let go-coolant flow should increase-if not we need to check out this guide to help fix it

https://www.2carpros.com/articles/car-heater-not-working

Please run down this guide and report back.

Like the above I have no heat in winter. If I take it to the dealer and they fix it I get no air conditioning in the summer. I've about replaced everything. Fan blows, thermostat works just fine. Problem is that somewhere in the vent system there is a flap/door/something that isn't opening when I move the switch from heat to cool. I'm about to start taking things apart. Dealer is having fun, and making money, flipping it back and forth every time the weather changes. Where's the flap?

I believe you are refering to the blender door. It is located near the heater core, and is actuated by vacuum.

I own a 2000 chrysler 300M. The heater doesn't work. The fan/blower is working and the air conditioning works. The lines running in and out get hot when the fan is on and set to heat. I have been told that its probably the door/flap that opens and closes The air works. I tried replacing the air/heat switch and that wasn't it. I was told it is likely the flap/door that opens and closes dependent upon whether ur using the heat or air. Is this the likely issue and if so, how do u get at this part in this make and model in order to replace it? Also, the lines running to and from get hot when the heater is on.

If both heater core hoses are hot, then the blend air door is the problem. It is a vent door located near the heater core (under dash) that opens and closes based on if you want heat or AC. Check the actuator. Most likely is isn't working.

My car has only warm heat. Coolant and thermostat changed last winter. Air conditioning works in summer, car does not over heat, car warms up relativly fast, but just has warm heat. Coolant level is fine. car has climate control . Can you help?

There could be 4 causes for your problem. I'll list them in order of most probable.
1-Thermostat for climate control malfunction.
2-Blend door for heat/ac not going completely to heat position.
3-Partcially plugged heater core.
4-Engine thermostat defective or not a hot enough stat. Even though the stat is only a year old, it could still be too cold a stat or defective. I would check this first. I could be a cheap fix.

I have no heat in my car. They have flushed the system, checked the hoses, nothing wrong. The blower works, but blows out cold air. I am running out of trys. Could you please help me.

Lets try replacing the thermostat with an OEM part and see what happens-its job is to control engine temperature

We changed the thermostat. Still no heat. Flushed the system again, no heat. the hose are hot. ?????????????? I need heat!!!!!!

Is the blower motor operating and blowing air out of the vents-if so probable causes air mix/blend/mode doors-vacuum/actuators inop. If not could be the blower motor itself, blower resistor,relay, and HVAC module-

The blower motor is working, but blowing out cold air. How hard is it to replace the air mix/blend/mode door, vacuum/actuators?

The car is running at proper temperatures, heating up but not overheating but I'm not getting heat into the cab

check your actuators in the heater box.generic pic enclosed. these can be either vacuum or electric operated.