Auto A/C temp not working right

[Postalsnap]

I've got a '98 Explorer Eddie Bauer with the automatic climate control. In the winter it worked great. I set it at 73 degrees and cruised. Now that it's hot here in Houston, Texas (90 outside temp), the automatic setting isn't so automatic. If I set the temp over 68 degrees, the fan kicks on full blast with nothing but 120 degree heat. The A/C doesn't kick on until I take it to 67. During the cold months, it would mix outside air with heat to make it set temperatures.

At first I thought it may be low on freon, so I gave it a shot of 134a which makes it blow REAL cold. But I still have problems with temp regulation.

Is there a temperature probe/sensor on the inside of the cabin that may have malfunctioned? What could cause the absolute total heat or A/C. There's no inbetween anymore.

 

[RiverRat]

It could be alot of things. It could be the "base" a/c system. There is an in-cab temp sensor. But today i'm guessing you have a blend door issue. You could self test the EATC control module.

 

[Postalsnap]

Test EATC???

How do I test the EATC control module? I've got a Haynes Manual but nothing really in it on troubleshooting the A/C system. The mixing/blend door is an interesting notation. It's got to be a "control" issue because when I cross that "threashold," the heat is either all the way on, or all the way off.

 

[Postalsnap]

In cabin temp sensor?

Where is the cabin temp sensor?

 

[RiverRat]

I think you can test the 98 without using a scan tool. Try pressing off and floor. Then within a second or two press auto. It will self test and codes will dislpay on the screen.

The in car temp sensor is in the little "vent" to the right of the radio.