Have a single speed Lennox furnance that the air handler has at various times continued to stay on after the temp. has been satisfied (generally for 10 minutes but has to kill power a couple times to make it turn off). We have no humidifier on the system so it typically just shuts off after temp is satisfied. Also, the condensor has started to turn off at random times prior to the thermostat being satisfied. Today the air handler shut off but the condensor was still running. Any ideas as to where to look to for the problem.