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Hello, set the thermostat up to 90F and tell me if stage two stays on or not. Tell me if your thermostat has an outdoor air temperature sensor attached.
We can go from there.
Thanks, ***** ***** most likely correct, however I need to see the unit wiring diagram to determine which limit you are tripping.
Hello, it is most likely a problem with printed circuit card thatsends control signals to the blower motor.
Please attach a well focused, close up photo of the wiring diagram glued inside the service panel, the picture needs to be taken from straight on, in very good light.
You can use the paper clip- icon at the right end of the tool bar at the top of this dialog box to attach it here.,Include a picture of the thermostat wire connections to the printed circuit board in the same area.
If there is no paper clip-icon, look for the '+attach files' link at left of your send button.
I can mark it up with trouble shooting instructions.
delete this please, it slipped in from someone elses answer somehow
"Hello, it is most likely a problem with printed circuit card that sends control signals to the blower motor."
Hello again, sorry, the internet has slowed here a bit.
Thanks, ***** ***** that the combustion chamber pressure rises beyond the allowable limit for the HPC (high pressure switch) to stay closed, due to a restricted exhaust vent, or partially restricted condensate trap, or exhaust blower blades loaded with soot....... or just a bad HPC.
Let me know what you can figure out, we can go from there.
The high temp switches are in series so if either trips, the burner shuts off, and what happens with the blower after that is incidental.
The two stage pressure switch puts the gas valve into higher flow mode when it is closed, that also results in ramping up the blower motor to a higher speed, this is why we are testing these items.
If you try guessing or making assumptions prior to testing you can end way off into the tall weeds and waste a lot of your time. Testing first eliminates the guess work, a 'failed' test is as good as a 'successful test' each rules in or rules out a range of situations,
beyond *these tests there is a very wide range of other things that can go wrong, it would take hours to write all that up for you, and even then would difficult to comprehend for most people.
This testing approach is the most efficient.
You are not stuck with me by the way, we have a few dozen other experts here who will answer if they feel like it.. let me know if you would like me to opt out or not, I do have over 51 years and thousands of successful trouble shoots under my belt, generally speaking, I know what trouble shooting approaches work best.
Fit the jumper long enough to get a result, either positive or negative, in this case to see if the burner and/or high speed fan stays longer than before,
those are the flame roll out switches, and you have dismounted one of them, no need to do that. There are basic skill sets involved here, without those it will be dangerous for you to work the furnace
I am going to recommend that you call one of the local furnace service companies,. if you would like me to search out a well rated one let me know which direction you are from the center of the nearest city.
Meantime remount the flame roll out switch that you dismounted.