reoccuring furnace problems
#1
11-25-12, 10:17 AM
reoccuring furnace problems
We have been having issues with our furnace inducer fan not shutting off and the diagnostic light flashing the pressure switch code.
We did everything we (and others) could think of to fix the problem: changed the pressure switches, checked intake and exhuast, cleaned header box, etc.
Since it is cold here and we need heat we turn the furnace off at the switch and re-start it. Doing so allows the furnace to run normally until the problem comes back.
So 4 days ago the furnace started running normally and has run fine for 4 days up until this morning.
What kind of problem can it be that the furnace will run fine or 12 hours, or 4 days with no problem and then have the problem reoccur without warning? When the problem does come back, it will not even run long enough to heat the house up before shutting off.
Why would the inducer fan shut off after the heating cycle for 4 days and then randomly stay on, causing problems?
I have no idea what could cause a reoccuring problem like this when the furnace runs complete normally and fine intermittantly.
We did everything we (and others) could think of to fix the problem: changed the pressure switches, checked intake and exhuast, cleaned header box, etc.
Since it is cold here and we need heat we turn the furnace off at the switch and re-start it. Doing so allows the furnace to run normally until the problem comes back.
So 4 days ago the furnace started running normally and has run fine for 4 days up until this morning.
What kind of problem can it be that the furnace will run fine or 12 hours, or 4 days with no problem and then have the problem reoccur without warning? When the problem does come back, it will not even run long enough to heat the house up before shutting off.
Why would the inducer fan shut off after the heating cycle for 4 days and then randomly stay on, causing problems?
I have no idea what could cause a reoccuring problem like this when the furnace runs complete normally and fine intermittantly.
#2
11-25-12, 10:52 AM
Banned. Rule And/Or Policy Violation
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In general, the inducer motor should turn on and stay on as long as the thermostat calls for heat, and should shut off when the thermostat no longer calls for heat.
The likely source of this problem is a thermostat that isn't actually shutting off the furnace or a circuit board that isn't shutting off the inducer motor --- with a bad circuit board being a lot more likely.
Do you have a multimeter and understand how to use it? If so, see if the voltage between C and W on the circuit board is turning on and off reliably when the thermostat is turning on and off. You should have 24 VAC when the thermostat is calling for heat.
If you have zero volts and the inducer motor continues to run, replace the circuit board.
In general, the inducer motor should turn on and stay on as long as the thermostat calls for heat, and should shut off when the thermostat no longer calls for heat.
The likely source of this problem is a thermostat that isn't actually shutting off the furnace or a circuit board that isn't shutting off the inducer motor --- with a bad circuit board being a lot more likely.
Do you have a multimeter and understand how to use it? If so, see if the voltage between C and W on the circuit board is turning on and off reliably when the thermostat is turning on and off. You should have 24 VAC when the thermostat is calling for heat.
If you have zero volts and the inducer motor continues to run, replace the circuit board.
#3
11-25-12, 02:12 PM
Tested with a multimeter. When the thermostat is not calling for heat the inducer fan is running and there is 24 VAC when testing between the C and W.
So there are 24 VAC and the inducer is running all the time, unless we shut the furnace power off.
So there are 24 VAC and the inducer is running all the time, unless we shut the furnace power off.
#4
11-25-12, 02:52 PM
Banned. Rule And/Or Policy Violation
Trace the wires that operate the inducer motor back to whatever circuit board they connect to. Post the make and model of the circuit board or ignition control.
You have a defective circuit board that needs to be replaced.
Erratic operation of equipment is fairly often an indication of a failing electrical part.
You have a defective circuit board that needs to be replaced.
Erratic operation of equipment is fairly often an indication of a failing electrical part.
#5
11-26-12, 04:18 AM
It is a Lennox Surelight circuit board from a Lennix G51MP-36B-070-07.
The furnace is running right now so I will post the model # etc. next time it stops.
I have been trying to get a circuit board for weeks but no one will sell it to me because they want me to have their tech come out and deal with the problem.
I appreciate the help and advice. Was not sure what was causing the erratic behavior as it worked fine last week after 2 weeks of not working.
Now to find a circuit board.
The furnace is running right now so I will post the model # etc. next time it stops.
I have been trying to get a circuit board for weeks but no one will sell it to me because they want me to have their tech come out and deal with the problem.
I appreciate the help and advice. Was not sure what was causing the erratic behavior as it worked fine last week after 2 weeks of not working.
Now to find a circuit board.
#6
11-26-12, 09:26 AM
Banned. Rule And/Or Policy Violation
The circuit board or ignition control module will have the make and model listed on it. You may be able to find someone to sell you a control by Googling the make and model number.
