Thermostat Clicking on & Off every 5-10 sec.!

16:37 ______________________________________________________________________ My Honeywell T8600C thermostat clicks on and off every 5-10 seconds when it needs to increase the temperature. This sounds like a loud relay and lasts for 1-2 hours. We have a gas furnace. Our local HVAC service rep says the furnace is OK and cannot find anything wrong with the thermostat. I need your help. This is really irritating! Any ideas? (Should I just buy a new thermostat?) Thanks, DGM Replies: svctech1 “Re(1):Thermostat Clicking on & Off every 5-10” , posted Sat 8 Jan 23:08 ______________________________________________________________________ Is this a Digital t-stat with batteries inside. If so, checked the batteries with a meter to see if they are good. If batteries are low and no good, change them and see if that works. svctech1 SuperDave “Re(1):Thermostat Clicking on & Off every 5-10” , posted Thu 6 Jan 17:10 ______________________________________________________________________ Clicking that often is not normal!! The question is, is the furnace cycling on/off with the clicking? If so, I would bypass the thermostat to see if the furnace operates normally.. If it does!! Bad thermostat, if not something within the furnace is causing the control voltage is drop and maybe effecting the T8600 thermostat. SuperDave