Toyota RPM idle low
2000 Toyota corolla 5a engine rpm lowers when aircon is turned on.
The 8th generation (E110) of Toyota's best-selling compact car.
Shawn, probably a stuck A/C Vacuum Switching Valve. VSV increases idle when the A/C compressor starts. If it fails very low RPM idle when running the A/C.
You can find a good tech to diagnose and estimate repair or google search your make and model# VSV replacement.
I hope this helped you out, if so let me know by pressing the helpful button.