Your AC doesn't need a sensor to prevent it from freezing. If the unit is properly charged / parts are functioning properly the AC unit will not freeze. (running the system normally above 55F OAT)

Some designs that incorporate zone controls will include controls to prevent freezing, but that is only for zone systems --- not for traditional AC units without zoning.

If they didn't hook up gages to check refrigerant charge, you should probably find a new HVAC company to service your AC.

The freeze control can work (depending greatly on what is truly wrong with it & load conditions it is under), but it's not the proper way to do it. In record heat type weather I think the unit will have trouble keeping up. The freeze control will shut the compressor off to thaw the coil, once temp raises the unit will start again. Only to repeat the process all over again. That isn't a cure.

Your system needs to be investigated to find the cause, not just treating the symptom.

I service the Katy, Texas area.

That is my very same thought. The problem is still there that is causing it to freeze and this was just a band aid. Unfortunately I paid for this band aid because we will be leaving for a week on vacation and I didn't want the unit to freeze while we weren't there. I even asked the tech to hook up the gauges but he said there was no point because according to his other instruments and calculations the unit was working EXACTLY how it should be. I have a neighbor that I say hi to but never speak to them. He works for an HVAC company so maybe I'll ask him if he could check it with the gauges. The unit does work hard as it is a little undersized due to an addition I added about 6 years ago. On very hot days like we are having now it will not shut off until the sun goes down but usually stays within 3-4 degrees of the set temp. which is 70 degrees. Thank you for your response and I will probably call someone else to look at it after our vacation. One more note the temp coming out of the register is always within the 15-20 degrees rage of the return air.

If airflow isn't the problem then it's probably low on charge. Get a new company - they didn't check or diagnose anything!

I removed the filter to make sure it wasn't airflow but I know there is more to it than that. My unit is technically undersized apparently because of an addition I put on about 8 years ago or so. I'm right at the max square footage they said for my unit and they recommended I replace it but it was only 4 years old or so. I've had zero issue's with the unit up until these past 2 weeks. They just called me to ask about my experience and I told them the truth obviously. They are sending another tech tomorrow. I'll keep you posted.

I had a central AC that froze up once out of the blue. It was low on charge and had been leaking from the high pressure switch. Hopefully the second tech will hook up their gauges and determine the cause of the freezing.