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Re: furnace blower motor
I would check the "G" wire at the Thermostat and make sure that it has a solid connection. The other end screws on to a terminal in the furnace. Check this connection as well. This green(G) wire is what activates the 120v relay on the circuit board. You can test this by turning the thermostat to the off position and then jumping the 24v R terminal with the 24v G terminal at the furnace. if the fan comes on then the problem is in the thermostat wire or the thermostat itself.
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Really need more info but with what you have stated: many furnace blowers are set up to simply run the blower after a set time.
Yours is not doing that and is in a very unsafe condition. Only thing keeping your furnace from burning until it glows red hot is the over temp safety.
With the info provided I would suggest you replace the furnace control board and the abused safety. Verify blower operation before you call it fixed.
your ventor motor has to come on first to close limit switch,follow tubing from switch to ventor motor see iffu have 120 volts going to it, if 120 volts replace ventor motor assembley, no reset on board, board will reset every time u turn of power and back on
You have a short circuit, which is obviously dangerous. Your blower motor is controlled via a 24VAC control circuit, but is 120VAC. The circuit board and gas valve are probably history, but it needs to be troubleshot to determine the scope of the damage.If you remove T stat you will see several colored wires. The red and green wire when touched together should cause your fan blower to run. If that works when you bypass t stat the t stat is gone. The red to white will open your gas valve on your heater. The red to the yellow or blue will start your AC compressor or condenser fan motor. Be careful with the yellow and blue wires as one is actually a neutral and one goes to the AC contractor on your condenser unit contractor. Hope this helps!
Go to furnace and shut off power, remove blower door compartment. Inside you will find a control board where thermostat wires are connected. Should look something like this:
R-Red Wire= Power
G-Green Wire= Fan
Y=Yellow or Blue Wire=Cooling.
It sounds like you have a bad motor speed. So try this:
With Power Still Off, on the same control board there is a terminal usually marked Cool and Heat. There should also be a couple of terminals that are named park. The wires hooked to these are the fan wires..
Exchange the Heat and Cool wires on the terminal board. Put everything back together and try cooling again, if the fan comes on
then you have a burnt out motor speed. Go back to furnace and change
the heat and cool wires around, next if Cooling had the black wire hooked to it, put yellow or blue on Cooling and black to park.
Note: The reason why you put the blower door back on is because it
has a door switch that if not properly seated, you wont be able to power
Usually when the furnace blower motor runs all the time
The limit switch or rollout switch is usually open or bad.
The furnace board is seeing that one of those switches is open, so it brings the blower on to try to get the heat out of the combustion chamber area, so the switch will close. But if the switch is bad and won’t close, the furnace board will keep the blower running continuously.
This one is difficult to solve on line. I wish I could see the unit. First, check the diagnostic code chart on the inside of the blower compartment door. Constant blinking is the code for "normal no call for heat" or " normal call for heat". The diagnostic code chart will explain the difference according to the flashing speed. So this part may be ok. Second, disconnect your thermostat wires fron the furnace. If this turns off your blower you have either a bad or miswired thermostat, or a bad thermostat wire. If this doesn't narrow it down... then locate all of the wires coming from the blower motor.
If it is a "variable" speed motor the wires will be connected to the board by a module. Make sure the connector is plugged in properly. Check the dip switch settings to make sure you are not set for continuous fan.
If it has a "multiple" speed blower. Locate all of the wires coming from the motor. The two brown wires should be connected to the capacitor. The white wire should go to the neutral post on the board. The black wire will connect to the post marked "cool". Of the remaining wires... determine the speed by color according to the schematic. Place the desired heating speed wire on the post marked heat. The remaining wires MUST be connected to the posts labeled "park" or "spare". I believe that you may have mistakingly placed one of these remaining wires in the wrong location.
If none of this helps keep in mind..... just because the parts you changed are new, does NOT mean that they are good.
I hope this info helps you...
limit switch is on the heat exchanger black plastic about 1and1/2 in. by 2 in. with 2 wires going to it , it has 2 screws holding it in take it out and check it with an ohm meter and you should not have a reading if it is good