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My name is Billy.
What is the make/model of the unit?
does you system have a blendaire ventilation package built in with it?
thank you...so the inducer motor kicks on without a call for heat? and the main blower kicks on for no reason?
If you changed the control board..this can only be caused by a bad wire somewhere.
The inducer can only be turned on by a signal from the board. The board can only do this if there is a call or a bad limit wire somewhere.
When limit opens or a wire in the limit circuit, it brings on blowers as a safety feature. You will need to search all wiring starting at thermostat to furnace...and then the wiring in the safety circuit.
Usually this would be indicative of a bad board...but since yours is new.it leaves wiring issues.
the damage we are looking for (or switch) is the safety temp sensors on the front wall of furnace.
Whether it is a wire or switch...after board that is the only thing that can bring on the 2 fans
just respond when you can....I have also seen these units start the blower in summer because of too much heat in the furnace from the vent pipe in the hot summer sun...
Just sign back in when you are ready
just respond to one of the emails
sounds like board..but I guess a rogue wire could do this
ok, just keep this on your end until ready or the system forces a response from me.
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I am a different tech, I would disconnect the thermostat wiring to the control, see if it ever turns on by itself without the thermostat wiring connected. This would rule out the thermostat wiring or possible low voltage feeding the board issue with a false signal through ground from the thermostat wiring basically a backfeed of the circuit can cause this. I would do that as that would be the fastest way to rule out a board issue and to narrow down the issue. Often this is caused do to a thermostat grounding issue or bad ground at the board. Check it out and see.
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We already know the board is new..You already replaced thermostat wire.
The tech that popped in did not read what all you have done. The previous recommendation is not a logical way to proceed. To check things you have replaced already is silly.
If you want to keep on track as we were just disregard and stick with me. Just let the apprentice trying to get involved know we already have those things under control and you are continuing with me.
it is low voltage that triggers the high voltage. Pull a wire from a 24v limit and the fan kicks in...a loose wire in the safety circuit can trigger the fans,
When a limit opens the furnace "thinks" there is heat present and triggers fans by default.
good luck and keep me posted.
on the control board...tell me what color wires are on what terminal that come from the blower motor
Is there a chance you could post a pic of that?
thank you!...now we are on track...is the schematic on the furnace door panel clear enough for a picture?
and you are positive you do not have a blendair system where an exhaust on roof runs to keep home from creating mold?
as a test...remove the brown wire or pull off HEAT and tape...
then tell me if the issue stops
now put brown back.
Remove red wire from thermostat terminal strip on board terminal R.
Try same....NOTE, do not expect heat or cool during this but we need to know if blower starts
so how has it been thus far?
was this with R hooked up or not?
give me a a pic of the entire board.
we may have a harness issue....with R unhooked it totally eliminated thermostat and all thermostat wiring...and no 24v input to board...
no pics yet
the large plug on the board...remove an inspect the metal connectors in the plug...push all wire in...look for any white powder, rust or burnt points...
I can tell you that the issue is in the furnace and not external....
you may want to bypass each limit also to see if one is opening and tripping blower.
remove the W wire that mounts on circuit board from thermostat.
does it still cycle on 3?
ok it is getting narrowed down....your air switch..is it a pressure switch with a rubber tube or is it w ires going into the side of the exhaust motor?
unhook those 2 wires that come from the air switch and tape off separately then try again
only if it were heating...the circuit is open when the exhaust fan is off.
The circuit should not be reading closed when exhaust fan is not running. Unhoooking this will have no effect in cooling
I am wondering if the pressure switch micro contacts are making connection and bringing on the blower....this is in the safety circuit and could be the entire issue.
A bad pressure switch
put everything back in place except pressure switch wires...and lets try again,
That includes putting heat leg on and unjumping limits
what is 2 flash code?
could you please post a pic of the exhaust fan motor and pressure switch?
Ok I see the pressure switch..but not exhaust..
In thermostat there is not a wire on B terminal is there?
It codes that the pressure switch circuit is closed.
And this is with the pressure switch unhooked.
Folloow the 2 wires from the pressure switch to the board.....if there is no connection between those wires before they get to board...short, another control..then you have a bad board...even if it is new.
If it thinks the pressure switch circuit is closed when it is not even hooked up..then the board has a defect.
lets unhook the gas valve wires...there is something shorting somewhere..but it takes a call on w terminal to get 24v to valve.
So lets drop the gas valve out...and lets see what happens
you bypassed pretty much everything that can start the blower as far as safety switches....is there a snap disc switch that maybe we didnt get?
you can unhook but you would have likely noticed the unit on . hot, limit open etc..
This one is surely a tough one
just keep me posted..