Furnace runs OK, but blower runs again a few seconds later
Happens more when cold, as in the morning or real cold outside temps. Furnace will run & heat normally, but after it shuts down, the blower will start up a few seconds later and run for only a few seconds. Usually once, sometimes twice in quick succession. Furnace is Carrier forced air, about 18 years old. Technician states ''that is what old furnaces do'', cleaned it, checked plenum for cracks, all OK.
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Re: Furnace runs OK, but blower runs again a few seconds...
Could be a defective thermostat in the plenum.
When a gas furnace shuts down the fan(blower) will run until the plenum cools to the safe range. Usually 1 and 1/2 minutes.
Intermittent operation is a defective thermostat or relay.
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Sounds like the thermostat, the way to verify is to unplug indoor unit, remove thermostat, take pic of wiring with phone or label the wires as to the terminals. Carefully twist the yellow,(Y) Red (R) and the green (G) together. Plug the furnace back in, if the unit operates normally, replace the thermostat. I am basing this on the fact that the blower speed is changing. This could also be an anomaly within the circuit board in the furnace section, not likely though as the outside unit (condenser) is not controlled n by the indoor board unless this is a heat pump. hope this helps. D
To avoid all sorts of wiring problems use only one two stage heat thermostat and wire outdoor boiler to first stage of heat or disconnect white wire from original thermostat and run 2 wire thermostat cable (white and blue , Heat and common to control outside water furnace control ) from original furnace to outdoor 24 v furnace relay .
Hello, this sounds like a flame sensor issue or high limit switch problem. First, turn off power to the Furnace and remove flame sensor, it is a small metal rod on the opposite side of the igniter, use some steel wool to clean it up and reinstall it. If that does not solve the problem then inspect you filter, blower wheel for dust or dirt, also make sure the blower motor is running at the proper speed. I hope this helps.
ok...where to start.lol ....the thermostat is just a switch.It will tell the unit to run or not run.if you measure the temp with the heatpump running,the air is warmer than 68 but it feels cool to you because your body is 98.6.The unit will run more often and for longer periods when the temperature drops outside for a few reasons.First,your house has more of a load to heat,meaning you have more heat loss because of the difference in temperatures outside and inside.Second,your heat pump pulls heat from the outside air.The colder the air outside,the less btu's for it to pull.If you have anymore questions email@example.com Hope this helps,Dave