hvac Blower Motor will not turn on.
I have a Lennox Hvac system that had the control board that broke. It said the the heat jets would not lite. The Fan would not come on anyway. I replaced the fan capacitor, it still did not work. I then replaced the control board. After that everything worked until the other day (a month or two later). It now will fire up, but the blower does not turn on. It will not turn on in heat mode or ac mode. When in heat mode it gives me an error "Roll−out switch open" I have tested both roll out switches and they both have continuity. I cleaned flame sensors. the fan motor turns freely and i cleaned that a month ago. Im not sure what is wrong now. The error is says there could be a blockage in the air flow. I checked and its fine.
Just because the rollout switch shows continuity does not mean that it is not bad. Considering that it is a fairly cheap and easy fix, I would reccommend changing the switch in order to fix the problem.
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if the unit is coming on but fan motor will not start up,the first thing you need to do is make sure its getting the proper power. check for loose connections. find the fan motor hot wire, and check to see if its pulling enough amps. there is a rating label on the unit with all that info,close to the fan motor and will say how many amps its should pull. if all that fails you may have a bad motor.
funny thing about checking amp draw. do it with door closed. I am pretty surprised at the amount of people asking questions on a diy site that don't have a basic voltmeter, let alone a multi-meter. this is what I would do.
1. by a multimeter.
2. turn fan switch to "on" on the thermostat. This will energize high speed on the fan control.
3. check voltage between high speed lead and common lead to blower motor. (if control board is in blower compartment, you will need to temporarily hold the door switch in, I use electrical tape)
4. if 110v present, go to step 5. if no voltage present go to step 100.
5. check capacitor with your new multimeter. don't forget to discharge. if capacitor is bad - replace, if not replace blower motor.
100. Check voltage between c and g terminals on control board.
101. If 24 v present, replace control.
102. if no voltage present, check voltage between r and c
103. if no voltage present, check control fuse
104. if fuse not blown check for 24v at seconday inputs to control
105. if 24 v present replace control, if not check for 110v to transformer.
106. if 110 v to transformer, replace.
107. if no 110 volts to transformer check blower door switch, then furnace switch, then breaker in electric panel.
In regards to the roll out switch. with power off, trace wires (in and out of a roll switch) back to the control board. pull one wire off board and check continuity through the circuit.
instead of tracing wires, you can look at the schematic, but if you can read a schematic, you already knew that.
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