Ac blows cold air for about 15 minutes then starts blowing warm air then starts blowing cold air again freon is full

check to see if ac clutch is turning off and on

TX valve freezing?

Are you sure the relay isn't getting weak? Try swapping with another.

Hello brad is my name,did you charge enough freon to the system,yes or no.get back brad.

I would and sometimes you have to hold the recharge hose down on the fitting with some pressure to get it to take the R134.

you have moisture in the system this causes your expancion valve to freeze up an stop working, thats why it works for sort time and when it de-freezes stars working again. you need to do a EVAC & RECHARGE with a good AC service equipment, specially attention to pull vacumm por at least 20minutes so you get all moisture out of the system.
Good luck

recharge to 25 to 40. it should be low in freon

too much freon is the same as not enough freon

Have an 04 mazda6 as well, AC seems to be the cars weakness. It takes 15-20 minutes till my car is ina driveable condition (Phoenix, AZ)

Take it in for a tune up, but I doubt the AC will be any better

Possible condenser.

The problem might be that you got out of freon gas.