2016 Hyundai Accent 100,000+ miles. About a month ago, A/C started to blow cold air initially and then would quickly fade to only blow hot. Remember over past year, year and half, where had intermittent, rare occurence, issue with A/C only blowing hot air for a short period of time. Specific incident happened when idling stuck in traffic on interstate. Took to mechanic and was told compressor is bad and system needs to be replaced at about $1000.00. The mechanic said something about high pressure on the low side and low pressure on the high side indicating compressor is bad. Like this mechanic and used for several years with reputable service. Could it possible be something else (cheaper) that is an issue? Maybe climate controls, fuse, etc. Is there a thermostat of sorts that could be faulty telling the A/C not to cool?

 

There are tests and procedures to verify if a compressor is defective . At this point from the info you have provided, we don't know if the compressor is even engaging.
If it is , the diagnosis could be correct.
Before going any further we need to know if the compressor was being activated Can you get an answer from your mechanic?

It is not my intent to poo poo any mechanic or tech. Sometimes a customer doesn't always present the correct entire story,so we need to have accurate info before jumping to any conclusions.

 

Miser pays twice. If the mechanic claims, do you have any reason not to trust him? Make sure the compressor turns on. To do this, with the engine running in the parking position, open the hood and turn on the air conditioner. you should feel for a second how the engine took on the load from turning on the compressor, and when you turn on the compressor, it’s better to let someone stand by the hood and listen to the engine work. Maybe even a slight vibration will appear for a second, but then the electronics will even out the engine speed. So, if the compressor turns on, then there is some pressure in the system and the compressor is working. But the pressure may be outside the normal range. To do this, there is a special stand for testing the pressure in both circuits of the air conditioning system. It may be necessary to change the coolant in this system, which also costs money. If the compressor does not turn on, then either it is broken or there is no pressure in the system and the electronics understand this and do not turn on the compressor - a protective reaction of the system. Either way, it's a matter of pressure. At least that's where you should start. In my experience, it is cheaper to immediately replace the compressor and coolant, as well as all questionable seals and connections. Otherwise, as I said, pay twice...