Evap leak code?

Yes you can reset the light but every time you put the mode control in defrost the light will return even though you disconnect the compressor. You will have to get a wiring diagram and component locator to accurately jumper the switch connections for pressure sensing and make sure the compressor never turns on. HTH

I want to fix the problem not put a bandaid on it. But thanks for your input.

Then take it to a shop you trust, they may have to put dye in the system unless they have a 134A leak detector, with your rig at that age it could be seals going bad in the compressor or even a vibration fracture of a line, you just don't know until you get in there with the testers.

This is not an A/C code, it is an emission code. According to the scanner used it says first try a new gas cap, if not that then it may have an evap leak, which is emissions related, just trying to figure how the two tie together and what makes the code appear when the A/C compressor is energized and working. Previous owner never used the A/C because of the check engine light appearing.

It is possible that there is just enough drop in vacuum on the fuel vapor system to trigger the light, you should check for any minor vacuum leaks, I have seen the check valve leak just enough to set a code but not enough to cause any running problems. I had a similar problem on a GM product that had high miles but like yours ran very well, when the A/C and the brakes were applied the check engine light would turn on with a fuel vapor code, anyway too make a long story short I put a vacuum can on the vacuum line that fed the control vacuum valve to give it a boost, problem went away. real problem was the engine was not making enough vacuum to support all of the vacuum demands made on it. I don't know if this might be the same thing but it is a worth looking at.

DTC code P1456? or the P1457 which one?

I will have to check the codes again as I am not sure which one it was, sorry!