My gibson furnace is about 8yrs old and it was working fine heat was on yesterday morning but last night it stopped. Changed batteries in thermostat which in new(thermostat) but no heat. Checked the vents and no air was coming out. I took cover off furnace and saw that the red indicator light was blinking once every 3 seconds. what could be the problem??

Sounds like a over heat is holding the heat off taking to long allow a call for heat. A limit holding off .

There is a small silver rod situated in the flame at the last burner. This rod tells the board the flames are lit. Clean it in place with a piece of sandpaper or emory cloth and see if that doesnt solve your problem

I will assume this is a central air conditioning system. From what you tell us about the symptoms a few things come to mind for you to check.

1. Change your thermostat and see if that cures your problem.
*The following steps requires the use of a multimeter and work around electricity, use due caution or call a professional.*
2. Check the contactor inside the outside unit while you have the thermostat calling for cool and see if it is pulled in or if it is stuck. If you are not comfortable around high amp electricity then please call a professional in your area to make these checks.
3. Check to see if the thermostat wires going to the outside unit are sending 24 to 28 volts to the unit. This will tell you if the problem is outside or inside the home. If there is no voltage there then check at your furnace to see if the t-stat is sending the power on the Y connection.

There is much more to check but this should get you going in the right direction and will locate the problem in most cases.
Hope this helps.

Not sure what type of furnace you have but here a a few easy tips:

How to diagnose Robertshaw electronic pilot ignition

common furnace problems
Thermocouple operation
How do I light the pilot?
Transformers and Thermostats
Electric Furnace Notes
Millivolt valve/ pilot generator/thermopile operation
Wall thermostats



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I want you to do a simple test to verify that this is a thermostat problem for me. Start by removing the thermostat from its' mounting, next locate the red and white wire terminals place a jumper between them. If the heater now runs it is the thermostat went bad on you, if it does not run please check all connections both to the thermostat and to the furnace making sure that your wires have tight connections and are not broken. I am really leaning towards the thermostat being bad here. Sorry for the bad news but really strong feeling. Good luck

you the same person last night that posted .... my understanding is that you had a different type of thermostat originally with more wires on the old thermostat correct? from your post last night you have a heat pump system and this rth2300b thermostat is a straight cool straight heat thermostat... does it have batteries on the new one and does the new one not have a "c" terminal" post again what exactly was on the old thermostat color of wires going to what terminals on the old thermostat.. then tell me what you have for the new thermostat we can get you some heat... at worst case you should be able to jump out the red wire with the white wire at the thermostat and the heat should come on...you just will not be able to shut off without taking the wires apart but can get the house warm...

Hello,
From what you are telling me here, you have a loose wire inside the furnace. You could try giving it a bump again and it may work. But prbably not for long...
You need to find the bad wire or have someone look at it that can tell where the bad connection is.

Heatman101

you may need to replace the thermostat or the thermostat batteries if applicable. To replace the thermostat follow the instructions on the new thermostat. Make sure to set the thermostat to the gas setting(see instructions) this should cure your problem. Good Luck on the repairs

Dave

check transformer in furnace... thermostats get there power from it....not the room its in

Have you had furnace cleaned? Have you changed filter or took filter out and try heater? Have you checked return grill to make sure you don't have anything in front of it. Return grill or duct could be blocked or two small. Blower motor could be going off on thermal overload. Does the heater do the same thing when it is 20 degrees outside. The other thing it could be is furnace is not big enough.
Good luck let me know what you find out