AC light flashing and cricket sound post engine swap

Got a bit of a mystery on my hands and would love any input:

I recently got an engine swap done in my 2011 (long story involving a rock and a destroyed radiator). Same V6 4L as before just lower miles on it. Mechanic did a stellar job as far as I can tell however!... AC light is blinking when activated and blowing warm air. More concerning though is that the truck is also making a cricket like chirping sound when accelerating but that goes away after about 15min of driving. Occasionally the AC light will stop flashing and just blow warm air. No smell or other sounds to speak of. Maybe serpentine belt? AC compressor? Thanks for any advice!

 

Blinking light usually means low on Freon , have the system checked for leaks and recharge .

 

I believe a blinking light means a discrepancy between the engine (belt) speed and AC unit speed has been detected. Could be a clutch issue, a speed sensor issue on the compressor (think those are know to be faulty on certain year 2nd gens) or maybe not enough refrigerant like turbosnail said.

There's some good info about all of those problems on here.. I'll see if I can remember to dig up one of those threads later when I'm out of the shop

 

Kind of late response but check to see if the clutch is not engaging. My truck I had to replace the ac clutch a $30 part because the rubber breaks down after time