Heater not working properly?

My fan blows air but no heat. Even after letting my vehichle warm up I can drive 30 min. And still have no heat. Sometimes it will click in after 25 min. But that's not very often. I could always hear a click whenever the heat was about to start but I no longer hear that click. I've been told it could be a heat relay sensor. What do you think and can it be installed on our own?

I was having a problem with my heater not working; joined by an antifreeze leak. I have since had a new radiator, thermostat, and water pump installed. My heat still doesn't work and my car keeps overheating but when I go to check the coolant, it's not low. I also turn on the heat when the car overheats and even at that point; no heat comes out when doing that either. When the car overheats there is never steam or smoke either. I don't know what else to do and it's freezing where I live!

The heater in my caravan is acting strange! The passenger side is fine-it blows hot or cold depending on the position of the control lever but the drivers side only blows cold air. I have backflushed the heater core already to no avail and I am wondering about accessing the actuator doors. Is this a huge repair and what componets are involved? Any help you could give me would be appreciated!

We have replaced or thermostat twice our 2005 dodge caravan it blows cold air still! After quite awhile it will heat up. What do we try next?

The temperature gage indicates engine is at operating temperature, but the front interior dash heater blows cold air. What is the problem?