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What is the model number of thermostat? What type of system do you have, (ie: heat pump, A/C)? It sounds like the thermostat has not been programmed properly and the dip switches haven't been set for the proper mode of operation.
module RTHL3550 I have a Gas ferance with A/C I have set up the thermostat by the manule and check the setting 5 times to make sure I did it right there are no dip switches
I'm Not sure which manual you are using. If you are using the small red user manual to set up thermostat you will need to get the installation manual to program the thermostat for gas heat with A/C. If you don't have this manual you can download it from honeywell.com, or type the manual number in your browser; Honeywell 69-2584ES. You will see a PDF of the Quick start installation guide. If the thermostat is indeed programed properly, you probably have a problem in you gas furnace. There is a limit switch on the fan that will cycle the fan back on if enough heat builds up in the heat exchanger after it cuts off. Could be due to a defective limit switch but also other problems; such as air flow, stopped up heat exchanger. Have you had your furnace serviced by a heating service company this year? If not I would suggest that you do.Â There are a number of problems that will cause the issue you are having and It is diffucult to troubleshoot the cause without actually being there. I hope this helps. Please let me know the outcome and if I can give you anymore advise.