Okay i have an 2008 avalanche LTZ, no rear air.

i know this is tahoe and suburban thread but its the same system!

A few weeks ago the fans started to erratically turn on, maybe 10 seconds after start up.
I also noticed the ac light flashing, and compressor not engaging. these both seemed to resolve after driving some miles.
Now the ac light is blinking and compressor not engaging for more prolonged times, with maybe turning on automatically for 5 minutes over a 45 minute drive
the fans are still erratic.
When the compressor is not engaging there is no power at the fuse for ac or the ac compressor relay, or at the ac compressor.

I replaced the condenser that had a slow leak (always maintained freon)evacuated the AC system recharged it, changed the low pressure switch.
I changed the fan relays, no change.
i disconnected battery, held snow flake, held snow flake plus recirculation button
my engine temp is accurate, out side air temp is accurate.

i am going to try to change the ambient air temp sensor next.
Kinda stumped

any advice, or something obvious im missing?