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Re: switch sticking on furnace blower
Start by turning power off .clean contacts on switch then buy some dielectric grease put it on all moving parts even in contacks .or you can use graphite lubricant powdered .both can be found at hardware or auto parts store .had same problem
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Since you have two thermostats that operate the heating unit and the fan, and the fact that neither will turn the blower on, I would suspect the furnace/ air handler. Turn the thermostat to heat and see if the heat and the fan comes on, if it does operate normally in heat, the fan relay or the high speed on the blower is most likely the culprit. (If the furnace is equipped with a circuit board, the fan relay is integral to the board, if it an older furnace it has a separate fan relay). If it does not operate normally in the heating mode, verify power to the furnace, see if the flame comes on, if it does: the fan motor, circuit board or the fan relay are most likely the cause. hope this helps!
The 5 amp fuse may be bad, they go quite often, and they are exactly the same as the car ones. Check the fuse with a meter. If its OK turn the unit on and check for voltage going to the blower fan. You should get a reading between at least one pair of wires. The unit should have a schematic on it somewhere, check it to see which wire pairs are used for the variable speeds of the fan.
Have you checked to make sure that all of the supply registers are open, the air filter is clean and nothing is blocking the return air grill?
It almost sounds like you could be cycling on a limit switch.
Usually on gas furnaces, the blower is controled by the onboard controls, in the cooling mode the thermostat will control the blower.
I would be looking past the thermostat, at the furnace it self.
I hope you find this helpful. If you continue to experience problems, please let us know and we will dig deeper. :)
You need to check if the air handler fan running.Suppose if you donot see it then, check to see if the fan on the outside unit is running. If the fan on the outside unit is not running either, check to make sure that the breakers for the furnace/air handler and the air conditioner are on. Also if the breaker is not tripped, then the problem may be your thermostat, the furnace/air handler control board, or the wires between the furnace/air handler and the thermostat.
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sounds like your not getting a low voltage signal to the condenser, if your Air handler is in the attic check your secondary drain pan it might be off on the float switch, if your air handler is in a closet you need to check your float switch, it will have some wires coming out of it. Hope that helps you get started.
If you have a standard thermostat the fan switch is for the air handler only. It completely over rides the thermostat for most settings. Now lets see this is what I'd expect: fan switch on Indoor fan runs all time Fan switch auto Indoor fan only runs when thermostat is set to cool or heat and the thermostat is turned up above room temp for heat or below room temp for cooling. In both of these modes the furnace blower comes on and stays on til the room temperature is satisfied. The outdoor unit only comes on for AC the out door unit will not come on for heat or the "on" setting on the thermostat. See exception 1 & 2 below...
Exception 1- (in a heat pump the out door unit runs in both heat and cool mode
unless it has emergency heat turned on then it will not come on outside
in the heat mode, and depending on the type of heat pump and furnace or
air handler it is). A heat pump thermostat usually has "backup heat" and an "emergency heat" setting switch on the thermostat. Exception 2 - On some thermostats they are made to cycle on the heat if the temperature reaches a preset temp (around 50'f usually but definitely by 40'f). This mode prevents freezing when if instance the homeowner is away or while the home is under construction. In this mode the fan inside can run but the heat usually comes on with it. Exception3 - On some electric furnaces the heating strips may be individually controlled and thus not all come on at one time. This may give the feel of no heat especially if the room is cold.
Now there may be other exceptions but Ive tried to give you a heads up on some of the most common ones. If you need more help please post more specifics about your unit/system as to for sure what switches are set to what setting and what is happening with each. My first though was that maybe your system is OK and you needed to know if the thermostat was working properly.
If this helpd you understand your problem would you please give me as hifgh a mark as you can. Thnaks for using fixya and good luck.
If you have a volt meter, remove the thermostat off from the mounting plate and check for 24 volts AC across red (R) and White (W). Then check across Red and Yellow (Y). If you do not find any voltage, follow wire as much as you can all the way back to the air handler that is connected to it. Look inside and see if there is a small Auto (car) type of fuse in the wiring harness. Test and replace if necessary. Jump out the Red and Green terminals on the air handler and replace the door. See if the blower turns on. If so, you have narrowed it to the wiring to the thermostat. If not, you have a power problem and will need a technician.