I have an 07 expedition and the heater works but when your sitting idle it blows out Luke warm and only blows out hot while driving or pressing the gas? Could it be the heater core? It also has 115000
That's usually a sign you aren't getting enough coolant flow through the heater core. Could be caused by 1) low coolant levels, 2) blockage in the heater core, 3) water pump going bad. When you accelerate your water pump is working harder and able to provide more coolant flow to the heater core, so that may be why you get heat then, and not when at idle. Check coolant levels, if good then a simple coolant system flush might remedy your problem. If you suspect the core is blocked you can remove the heater hoses to it and flush it directly.
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