Most likely this is an issue with the blend door. This is a very common problem on the Explorer and a 98 is about due for the failure. Check heatertreater.net for diagnostic information and a fix.
From 1995 to 2001 Ford Explorer 4 doors it is a rotary dial on the left side of the CENTER STACK of the dash. From 2002 to 2005 Ford Explorer 4 doors , there are 3 vertical push buttons on the right side of the CENTER STACK of the dash From 2006 on, Ford Explorer 4 doors, there are 3 horizontal push buttons on the CENTER STACK of the dash located above the heater/ air conditioning selector dial. (Helpfull)
There should be a dial on the front of the heater that you set the temp. with.
BIOSPHERE
biosphere
biosphere
The plenum door is inside your heat/AC system near the heater core. It opens and shuts incrementaly to allow the heater core to heat the air passing by, or closes to keep passing air from heating at all. If you open the glove box on a 95 explorer, you can see the plenum motor... and you should be able to see/hear it moving as you adjust the temperature control dial from cold to hot.
On the gas controller there is normally a dial that is connected to the aqua stat probe and by turning the dial to HOT or cooler adjusts the output temperature
I was struggling with this myself.. You might have got your answer already, but in case you haven't... Turn the middle dial to zero (the fan control) and pull on it with some pilers. You should probably wrap then with a cloth as to not scratch the dial. You'll see the bulb and have to use some needlenose pilers to pull it out..
Just turn the dial toward you and pull out. Then turn the dial away from you to change the date (you can only go upward in date). HTH
I sure hope you don't kill any relatives for the insurance money after posting this request. Even if you are bllnd you can find the dial.
The Aztecs used a sun dial. Being a sophisticated race they realized that the Earth revolved around the sun. When the shadows on the dial had moved, they knew that the time had changed.
heater switch needs replaced