2007 Odyssey EX.
The ac compressor is on all the time unless I turn the heater OFF or set the heat to the maximum setting. Well, I'd like to just get fresh air with the fan on without the AC on. The AC is dragging on the engine and reducing mpg. I only want the ac on when I turn it on, not all the time. Is there any way to change heater/ac control behavior?

 

There should be an AC compressor clutch relay in the engine bay fuse box.
Pulling it out should disable the AC compressor
Or there may be a fuse that can be pulled which is a little easier to do

 

I was hoping there was one of those countless "tricks" of holding certain buttons, while pushing others. I would like to turn the AC on when I need it (only about 2 months a year in this climate). What I would like is to rewire the controls so the AC button turns the AC on/off and that's it.

The "AC OFF" vs "AC ON" on the display only applies when the AC button is pressed. The AC compressor is still ON when the display reads "AC OFF".

The manual states the heater/ac should never be turned off for any length of time to prevent moisture and mold buildup. Well it all depends on the climate. There certainly no one solution so the auto settings just don't work here.

 

No tricks.
Check the relay to see if it is stuck on.

 

relay appears to work okay.

 

There is an AC compressor clutch. That may be stuck on and the compressor is stuck on??
Can not tell from here.

 

"The ac compressor is on all the time unless I turn the heater OFF or set the heat to the maximum setting."

this means the relay is okay, the clutch is okay.
If the clutch was stuck on it would be on all the time. not the case.
If the relay was bad, it would be on all the time or off all the time. not the case.

I've concluded it's just a lousy design. I'm looking for a Kia to replace it.

 

The HVAC control unit take your input to turn on the blower motor fan and turns on the compressor.
If the compressor is turning on all the time then could be the control unit that is faulty?