heater

There might be an air flow regulating issue. Maybe the heat selector flap regulator is bad and won't move the flap to close the cold air flow from the evaporator and open it from the heater core. Those parts are under the dash, sometimes the access isn't easy, but that's where I'd start. Zee

I have the same problem. Paid $100 at 2 garages to find out that the heater valve is stuck.

Sounds like you have a bad actuator! It changes the flow of air. Locate the actuator, should be under dash and remove it. You should be able to turn the shaft with your hand. Turn it, til it stops and check to see if you have heat. If so, replace the actuator and you are in business!