I think that my mother has a bad thermostat. When the A/C is turned on, the furnace blower works but not the outside unit. However, when I press the contact switch (outside), both the compressor and fan come on. This would seem to indicate that the proper signal is not arriving there.
Mom always had problems using the old 5-2 programmable thermostat, and the buttons no longer work, anyway. I would like to install a simpler thermostat so that she can easily set a target temperature and select heat/cool/off. Is there any reason this can't be done? When I installed the programmable thermostat many years ago, the old wire colors were different from newer configurations, so I know I would have to be careful in that regard. There are 4 wires- red, white, green and blue (yellow).