On my AC/Heater panel, when I turn the dial to the right for vent/floor heating and I turn the heat dial all the way to the right for heat, the A/C automatically comes on with no heat. The faster I go on a highway the more heat comes thru, but driving on side roads the heat goes away and gets cold. If I keep the system turned off, and turn the heater on, there will be heat for about 30 seconds before it gets cold again. The Thermostat and Expansion Tank have been replaced and hoses have been flushed out. Yet sometimes it seems I can smell the heating coolant when opening the hood. Any suggestions?
Have a pressure test done. It sounds like you have a leak somewhere. That leak is allowing air into the cooling system, and the resulting air bubble is keeping the heater from working correctly. It may also cause engine overheating problems.
Tardis, thank you for replying. Funny you mention a pressure test. Sometimes when looking at the engine, I notice the expansion tank is low, a smell of antifreeze and also have noticed steam comming out from behind the fans. My thought was that there is a very tiny whole allowing steam to get through the radiator some how. It has never been replaced. I was going to replace it anyway… Sound good?