ck eng lite came on. tested at autozone was told the eng water temp switch was bad. temp gauge works fine. does this sound like good fix?

You don't mention make, model, or year, but most vehicles have separate senders for the gauge and the ECU.

I no longer recommend people have auto parts stores read their OBD codes. They can pull the codes as well as anybody else, and can tell you the code definition, but that is a long way from knowing what is going on. Most codes that mention an O2 sensor are not caused by a bad sensor but auto parts stores will sell you the sensor anyway. There are five different OBDII codes for engine coolant temperature sensors and none of them say the sensor is bad, only that the results are not right. For all we know, there may be a problem with the coolant level or a bubble in the coolant or a bad connection. The code says what sorts of areas to look in, not what is actually wrong.

The best approach is to take it to your mechanic. He will figure out what is going on more quickly (and inexpensively) than random parts guys will and he won't introduce new problems.

Take your chance, replace the ECT sensor and clear the codes. No joy, time to see a garage with a scanner.

I'd want to hook up a mechanic's scan tool to see what the ECT sensor for the PCM is actually reading. There may be more than one ECT sending unit. One for the gauge and one for the PCM.

I wouldn't let a parts sales person diagnose my car.

The temp switch RARELY goes bad, and I'll bet real money the trouble code didn't say that. What it most likely said is that the engine coolant temp READING isn't where the computer expected it to be and THAT is usually caused by a bad thermostat. This is why you never get repair advice from clerks making $7/hr.

Fix it before something worse happens.

I would have them clear the code and see if it comes on again.