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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7751
Experience:  Furnace, A/C and heat pump specialist.
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Freedom 95--exhaust fan comes on--burners kick in--then

Customer Question

freedom 95--exhaust fan comes on--burners kick in--then system shuts down--will repeat and sometimes fires up--sometimes system locks up with 2 led flashes
replaced flame sensor--works fine with burner box cover off--has same failure as before with cover back on--all vac switch hoses in place and orifices clean
probably not a good idea to leave cover off
any thoughts?
Submitted: 11 months ago.
Category: HVAC
Expert:  Heath.M replied 11 months ago.

Hello my name is ***** ***** will be my pleasure to assist you. It sounds like it may just be a dirty flame sensor. If you locate the flame sensor and take it out and clean it with a piece of fine grit sand paper or scotch brite then put it back in and reset the power to see if the burners will sustain flame. It is located in the burner section of the furnace and sits in front of the burners it has a single wire going to it usually located on the left side of the burners. You may have to take the cover off the burners to get to it will be the cover with the glass hole in it held on by a few 5/16 screws.

Customer: replied 11 months ago.
already cleaned the sensor--didn't help--so replaced with new sensor---didn't help--furnace runs great with burner cover left off
Expert:  Heath.M replied 11 months ago.

Is there an intake and exhaust on the furnace?

Expert:  Heath.M replied 11 months ago.

if the intake is not glue in place try disconnecting the intake pipe. You may have an issue where the intake air is cooling the sensor off.

Customer: replied 11 months ago.
exhaust is pvc pipe going out basement wall---air intake is room air from basement---everything worked well for five years--if the exhaust pipe was contaminated, would it cause the problem?--unfortunately it appears to be glued to the furnace
Expert:  Heath.M replied 11 months ago.

it could be the issue I would check the termination where it goes outside bees like to build nests in themand leaves and grass will clog them up.

Expert:  Heath.M replied 11 months ago.

its funny that the furnace runs fine with the cover of the burners off. It seems like it would get plenty of air from the intake if it is right in the room off the furnace. Be sure there is nothing blocking the intake either.

Expert:  Heath.M replied 11 months ago.

I will be off for an hour or so I will get back to you as soon as I get back on. Mean while check the intake to be sure it is not blocked and check the exhaust pipe outside. with the furnace running if you are outside you should be able to feel air coming from the pipe outside.

Customer: replied 11 months ago.
still not working--????????????????
Expert:  airheatman replied 11 months ago.

I am a different expert, Usually when these high efficiencey furnaces fail but will work with panel removed, the issue is a pressure switch issue.Removing the panel changes vacuum which operates the switch. Can you provide complete model on furnace (on label inside burner compartment)

Customer: replied 11 months ago.
I thought I was abandoned----model is AUH2C100A9V4VAA---checked exhaust--all clear--checked all hoses all clear--hose orifices are all clear--condensation outflow is empty--
checked continuity on first pressure switch---open with power off--kind of bouncy with system starting (and cover off)--yet it fires up and keeps going
you can put the cover on but let the top swing open maybe half an inch and it will still work--close the cover completely--NG
does seem like the switch must be a problem--unless the extra air into the chamber produces more of a flame for the flame sensor--but both the new and the old flame sensor had the same issue--and the old one worked fine for 5 years
don't know that much about pressure switches ---suppose the diaphragms go bad
Expert:  airheatman replied 11 months ago.

OK lets start by turning power off. Thermostat off. The power back on (This resets board). Then call for heat and tell me how far in sequence it goes and as soon as it fails, first error code we get.

Customer: replied 11 months ago.
system off--system on--exhaust blower starts--pressure switch clicks--igniter clicks and heats--gas goes on--gas ignites--after maybe 10 sec, burners go off--exhaust fan runs--then shuts off--sometimes it will retry and burners will stay on
error code is 2 lights (system lock out)this does not happen with cover off or even ajar by 1/2"
Expert:  airheatman replied 11 months ago.

Sounds like you may have a failing board.The issue with running with panel off is usually a pressure switch error, But if that is the case, the board should give us a 3 flash code. Sounds like board is completely bypassing any error codes and going directly to a lockout saying it has tried 3 times when it has really only tried once

Customer: replied 11 months ago.
when this started a month or so ago, it was producing the 3 flash error---not sure when it went to the 2 flashes
I can try and put the cover back on tight and see what the error message is
Expert:  airheatman replied 11 months ago.

Lets do that.Also make sure to turn high voltage completely off so board resets.

Customer: replied 11 months ago.
screwed in cover--turned off thermostat--turned off mains -
turned on thermo and mains--pushed door switch--fired up and didn't malfunction
released door switch--pushed door switch back on--went thru original malfunction process---did it again--same malfunction
still 2 flash error code
did notice that when it shut itself down--it was no longer calling for heat (slow green led flash)---a little stange
Expert:  airheatman replied 11 months ago.

This sure leans towards a failing board, but I hate to condemn without being onsite.I think I would call in an onsite the before relacing

Customer: replied 11 months ago.
I guess it could be--but the open cover doesn't compute
any chance there would be an error in the thermostat signal--probably not
also if the pressure switch was intermittent---then the system would shut itself down---what's the probability a new switch form northamericanhvac ($75) would fix it--gotta be cheaper than a service call--if I could even get somebody
Expert:  airheatman replied 11 months ago.

Not saying definitely pressure switch can not be the issue, but if it is, the board is still failing to do its job by giving the pressure switch error.

Customer: replied 11 months ago.
no clue--you are the expert---have an onsite contact with his own trouble shooter on vacation for a week or so---I will try him again--and in the meantime order another switch
Expert:  airheatman replied 11 months ago.

Everything points to board,since it is not showing a pressure switch code, but goes straight to lockout saying it has attempted max number of times on first failure. These boards can be a few hundred bucks is why I hate to tell you to buy board without being onsite. Sometimes onsite I may see something obvious that I do not see via internet

I often see so called experts on online sites that tell people to replace board or replace inducer, etc as a guess.Then if that does not prove to be the issue, customer is out all that money and upset.I have been in this business since 1974,but do not like guessing.

Customer: replied 11 months ago.
the old furnaces were a whole lot simpler--had a Williamson(?) for forty years--could fix it in about 20 min
will touch base later
thanks, ***** ***** Christmas
Expert:  airheatman replied 11 months ago.

Exactly all you had was a transformer a couple of relays, gas valve and a motor.

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