When I left for work the thermostat indicated low battery, the a/c was on and working.
During the day I got a call that there was a bad odor in the house. When I got home the a/c was off. I replaced the batteries in the thermostat but the a/c did not come on. I tried the heat, it did not come on either. I reset the main circuit breaker, still nothing. I noticed that the green wire inside the thermostat was not connected so I reconnected it. Still not working. Should I try replacing the thermostat or call for service?

Did you replace the batteries correctly. + and -. Usually a battery thermostat will work once the batteries are replaced. Kill all power to both the inside unit and outside unit for 5 minutes. Reenergize and check for proper operation. If not working correctly call for service.