Defroster is spitting out frost

oh well , nobody s perfect…

For what it’s worth anyway, the low side pressure is roughly equivalent to the evaporator temperature. If the low side starts flirting with 30 PSI too much then things can start freezing.

The operating pressure of refrigerant at the evaporator is nearly equal to the F temperature. If the evaporator pressure drops below 30psi and there is any significant humidity ice will form. Cycling clutch systems are designed to shut off the compressor when the low side drops below about 40psi, using pressure as a thermostat trigger. Expansion valve systems operating at low ambient temperatures can ice up in cool weather and more so if slightly under pressured. I have never seen a system ice over due to over filling.