My Carrier programmable thermostat has no display indication. I openned it and tightenned all wires. I also turned the power off and on to see if that would help. It didn't. I had this similar problem a two month ago but the display came back on its own. Please help. It's hot in SC.

1st buy the right tstat for your system
2nd ,be sure to mark/tag each wire as you remove so you will remember what color wire goes to which post
3rd re-install each wire to to correct post in your honeywell tstat
Follow instructions with the new tstat as to the setup and programing

If the thermostat is preventing the unit from running/blank screen then the first thing you need to do is make sure the main power is turned on to the system components both inside and outside. Then once you have proven the system has power you need to check to be sure the 24 volt low voltage control power is available. It could be a bad thermostat as you figure it to be OR it could be a lack of 24 volt control circuit voltage causing the thermostat and other controls not to work.

Before you start replacing parts like the thermostat you need to make sure that the control voltage as well as the operating power is available, Then if all the power sources are present it is a good possibility the thermostat is defective.

Usually a quick test is to jump the R (RED) wire to the G (GREEN) wire that goes to the thermostat. If both power sources are available the fan motor on the furnace or indoor air handler should run. NOTE: the above info is for standard HVAC system control wiring and color code.