So twice now my A/C won’t blow cold air after having the heater on for weeks, except if I run the defroster for a day or two then the A/C will blow cold air again. Any ideas on what might be causing this issue?

 

When it is no blowing cold - check to see if the compressor clutch has engaged and if so - the low side pipe will be cold (the bigger of the two ac pipes) and the high side pipe will be hot - sometimes too hot to touch. Low side should be 40 degrees or so -