AC unit is shutting itself off before reaching the temp on the thermostat. We have a wireless thermostat. Down at the furnace, the box also indicates that it has shut off the AC completely. It will run about 30 minutes at a stretch. Then stop for about 10 minutes and then come back on. It's putting out cold air but I haven't had the refrigerant checked in a few years.
Suggestions?

It sounds like the thermostat is to blame for this. There are settings on things called anticipators that oftentimes need to be adjusted. These settings tell or anticipate when the room will reach temp and fool the thermostat in thinking it has reached the room temp. Therefore not allowing the room to overshoot the setting on the thermostat.

Another thing that can cause this occurance is a device that may have been installed on the cooling system by the local power company. This device can shut the system down via a signal from the power company. This allows them to preven a brown out if to many folks are using to much power at a given time. Some times these little gray boxes that are fastened on the outside of the condensing unit on the outside of the house go bad and things start working wrong.

However my first guess is the thermostat is the device that has or is going bad. The thermostat will not regulate the on off cycles of the system if there is a refrigerant leak. And by the sound of it your not having this issue as it is cooling when it runs.
You need to find the manufacture of the control system being used or let us know the brand and model number and look into this further.

I'm hoping the problem has been found. Had a tech come out and check out the unit. Everything seemed fine.
We finally settled on the possibility that the Totaline wireless thermostat P474-1100RF may be getting outside interference. So I changed the channel and haven't had a problem since. However, it has not been 100 degrees lately. The real test will be during the next heat wave.
For now, it runs continuously until reaching temp.
The flaw in the theory is that the errant signal only shuts off the unit. It doesn't turn it on....so we'll see.
Thanks for your time. I'll drop a note when we heat up again here in Portland