Furnace question

[muddywings]

Tried for some heat today and no luck. Im 75% sure it could be a blower but don’t want to drop $100 if im wrong.
Lennox G40uh furnace
Two slow flashing lights
A/C works and i feel air in the vents (part of my confusion)
When i have ac on the blower fan (im pretty sure its the fan im looking at) doesnt run but as i said i feel air in the vents. See pic

Ask for heat and i get nothing
In heat mode i try the fan in on, automatic and circulate- no noise or movement.

Codes:


Confirm this is the blower in question and i aint smoking crack:




Best way to see if the blower is getting power?



Does the furnace blower operate in A/C mode? Or is that part of the A/C system that circulates that air?

Thanks

ETA: circuit board went bad about three years ago. Cant recall the symptoms but made me call for service vs trying on my own.

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[CobaltSkink]

I know there are HVAC pros on the forum, but that is the draft inducer.
The normal sequence for my furnace is:
1. Thermostat calls for heat, 2. the draft inducer turns on, 3. the burner lights, 4. the main blower fan comes on, 5. the draft inducer turns off.
6. Thermostat done with call for heat, 7. Burner turns off, 8. main blower turns off.

I wouldn't think a call for cool (AC operation) would energize the draft inducer; the main blower fan would run correctly.

I'd check to voltage and connections at the draft inducer. If those are correct, then I'd say the problem is the inducer. Do you have somewhere to buy the fan *today*?
Today, tomorrow, and Monday are supposed to be 80F. Are you willing to wait until Monday afternoon to install a new draft inducer?

[muddywings]

Im in no rush for heat.
Just want to see about fixing it.
Thanks.


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[Wulf202]

The blower is at the very bottom behind the circuit board.

If that draft inducer spins just for a second then shuts off its got a vacuum switch that can be cleaned and check the lines for leaks. Otherwise it needs a new inducer

[Walker2970]

Main Blower in in the very bottom... the upper blower you seem to be pointing to in Pic 2 is the combustion blower motor that should run in heat mode only.. as to the pressure switch it is possible it is bad and should be a easy quick fix... to test the combustion proof switch just jump the 2 terminals and see if it will light in heating mode*** do not run the heater like this if you are not watching the motor******this is just a test... if it is the blower it will be a bit more expensive if you are handy with a multi meter i can talk you through some checks. if it helps here is the manual http://0190acd.netsolhost.com/manuals/G40UH_Series.pdf

[bryjcom]

That's the inducer motor.

Couple of questions.

1. You said two slow flashes. Are they simultaneous or alternating?

2. Is you thermostat calling for heat?

The sequence of operation is as follows:

Call for heat at thermostat, thermostat sends 24 volts down white wire to board.

W terminal energized at control board

Board relay closes and sends 120 volts to inducer motor.

Inducer motor runs, pulls a vacuum and closes the pressure switch.

Pressure switch sends 24 volts back to board saying "I'm ready to start ignition sequence"

Board closes relay and sends 120 volts to ignitor for period of time.

Ignitor glows read and once that period of time commences the board sends 24 volts to gas valve.

Gas valve opens up, sending gas over the ignitor. Ignitor lights burners.

control Board looks for proper flame signal from flame sensor ensuring proper burner ignition

After approx 45 seconds of flame operation board closes relay sending 120 volts to blower motor to start circulating warm air.

[muddywings]

Thanks all

Will probably go with a service call.

But... two simultaneous slow flashing lights


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[bryjcom]

Slow flashing simultaneous is normal operation. Basically it’s waiting for a call from the thermostat

[CobaltSkink]

So, if it's operating normally waiting for a call for heat, maybe the call for heat from the thermostat isn't getting to the furnace?

[muddywings]

Slow flashing simultaneous is normal operation. Basically it’s waiting for a call from the thermostat

Hence theory on blower per manual 1.4.2:




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