started smelling burning on long drives, and now the AC doesn't work

Melting plastic doesn't really add up I guess an untrained nose could think freon oil mix might be plastic that would indicate you're evaporator is leaking and then shortly your air conditioner should fail usually in evaporator leak should leak out fairly quickly so if you still have cold air after all these smells it's probably not leaking gas refrigerant

 

No codes? If the A/C only stops when there is a code it is likely a failed or failing inverter pump. Especially if it works when the ambient temperature is low and codes when it is high.

The evaporators sometimes go bad on these cars. Actually I think it is a valve on the evaporator, but the difference is of no significance since the whole thing needs to be replaced. (On the Gen 3 they moved that valve into the engine compartment so it could be serviced separately.) PITA to replace an evaporator oneself and $$$ to pay somebody else for it. If it is the usual evaporator issue all the refrigerant will leak out.

Or it could be a leak or some other typical A/C issue.

In any case, if the A/C is not working as in, only cools poorly or not at all, do not run it. That may damage the condenser. More $$$.

 

The acrid smell of burning plastic is often caused by the inverter cooling water pump failing electrically. Eventually, this will blow the AM2 fuse and kill power to the dash and shut the car off. Quite the thrill when at highway speed!!

The pump is located directly behind the driver side headlight. It has potting material on the bottom, which is the material that heats up and burns when the pump motor is failing. I've had a few of these pumps that have had gooey areas underneath from the potting material heating up.

On another note, loss of the AC is also one of the early signs of the ICWP failing. If the pump isn't circulating coolant adequately, the inverter starts heating up. Since the inverter supplies power to the air conditioning compressor, the car will cut it off to help prevent overheating the inverter (reduces the current load).

 

If you could smell burning plastic it was probably in the hvac assembly under the dash. It could have been the blower or one of several air routing doors. Almost all compressor fails would have trouble codes as would many of the inside hvac devices.

The problem with the inside assembly is it requires an almost complete dash removal, a several thousand dollar job at most places.

I would invest $150 at a dealer to get it properly diagnosed and then report back for options.

 

My scenario will give NO codes, until the inverter gets hot enough to trigger the over temp P0A93 to let you know there's a problem