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  1. #1
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    Default force air gas furnace problems

    I have two problems with my gas force air furance (Armstrong Ultra 80 SX). The furnace is about 13 years old.

    I had an inspection and cleaning done on it a few days ago. The tech said that it looked like the heat exchanger was rotting and that I needed to replace the furnace. The diagnoses was based on a small amount of flame back burn (not all of the flame going into the hole) and a light brown residue powder coming out of the joint of the exhaust pipe.

    In the process of checking he neglected to remove a set of alligator clips from the control board (R and W). I did not realize this until I went to turn the heat on the next morning and found the burner off and the clips in place. I turned the burner on and removed the clips.

    The fans started working but the burner would not light.

    I brought another tech from the same company back. After checking all of the circuits and other parts. He found that when he disconnected the thermostat from the control board (by removing the R and W wires) the blowers would run constantly and the burner will not ignite.

    He concluded the control board was bad.

    My question is ... could leaving the alligator clips connected to the board overnight cause a short circuit of the control board?

    I thought maybe the clips may have gotten jostles when the fans started or the door was closed to close the circuit to cause a short.

    What do you think? Do you have any suggestions of other things to check?

  2. #2
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    Default Re: force air gas furnace problems

    foobar64 ....

    The wire labeled R is typically used to supply 24 volts AC from a transformer inside the furnace back to the thermostat.

    The wire labeled W is the heat turn on wire from the thermostat to the furnace.

    When the thermostat calls for heat a circuit inside the thermostat is completed joining the wire labeled R sending 24 volts to the wire labeled W then down to the furnace. The wires from the thermostat typically aren't wired directly to the controller rather to a junction point for all the wiring terminations inside the furnace. When the 24 volts is received at the furnace from the wire labeled W this usually goes to a relay which would then initiate the Induced Draft Blower to turn on first. Once that blower is up to speed and there is sufficient negative pressure in the chimney the negative pressure switch would close signaling the control module to turn on the igniter followed by the burner.

    I suspect while the technician was checking the furnace he removed the wire from the thermostat labeled W at the furnace. Instead of running back and forth to the thermostat each time to fire up the furnace he used the alligator clips to jump the 24 volts to the heat turn at the furnace. If the alligator clips were left in place when the inspection panel was replaced and the furnace safety override switch was closed .... the furnace should be running constantly.

    The first question is do you have an electronic thermostat?

    Next would be ... when you say the blowers are running constantly ... both or just the Induced Draft Blower?

    Did the second technician jump the negative pressure switch?

    You can try this yourself by disconnecting the two wires from that switch and touching them together while the IDB is running and there is a call for heat.

    Check to see if the rubber hose between the IDB and the vacuum switch is disconnected or has a split.

    In my opinion if there is a problem with the furnace not operating ... that company should be footing the bill for getting it operating back to the way it was before.

    Hopefully this helps.
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  3. #3
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    Default Re: force air gas furnace problems

    foobar,

    Gotta say that if the HE is indeed shot......any potential problems caused by the left-behind alligator-jumper wire seems kinda moot at this point.....unless perhaps you're thinking about replacing the HE instead of the whole furnace. Not sure if that would really be cost-efficient in the long run if this furnace is already 13 years old.

    I'll also suggest that you don't run the furnace in its current condition....if the HE has a crack or hole in it. CO is VERY sneaky stuff. It will make you very ill and can easily kill you while you sleep if the concentration becomes high enough. Or it can make you sleepy and then finish you off while you doze.

    I speak from personal experience. Never thought I'd get caught by CO in my own house, but it happened about 18 years back, IIRC. Was persistantly ill for a couple weeks one winter when I finally realized that it was something other than flu. (The wife didn't show any real symptoms as she was gone about 12- 14 hours a day, but I was here constantly while in the midst of a kitchen gut and remodel.) I bought a Nighthawk CO detector and it immediately screamed out a warning. Went down and inspected both the furnace heat exchanger and the flue on the gas water-heater. Sure enough, the furnace had developed a small hole in the HE since I'd inspected and tuned it up about two months prior.

    Regardless of what you choose to do concerning your furnace.....I'll recommend that you FIRST go get a quality CO detector such as a Nighthawk....if you don't already have one (or more). Avoid the cheaper brand units. Your life and health are worth the $50, I can assure you. If there are other folks in the house, theirs are too.

    Or you can buy a combo CO and gas detector unit. A few more bucks, but a very good choice and investment indeed.

    http://www.carbonmonoxidekills.com/
    Last edited by goldhiller; 11-04-2007 at 06:36 PM.

  4. #4
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    Default Re: force air gas furnace problems

    Hi DwarfWytch,

    Thank you for your reply, some additional info below.

    Quote Originally Posted by DwarfWytch View Post
    Am I understanding correctly? You were told you had a bad HtEx on a fuel-fired furnace yet chose to run it anyway? Likely it was tagged out and disabled (assuming it operated, albeit disfunctionally, prior to this visit) or wasn't functioning in the first place. Either way, your continued attempts at running this appliance are IMHO, unwise.
    Actually neither tech (same company) told me not to use or tagged the furnace. He just said that the heat exchange was likely going bad and that I should consider a replacement. He provided a quote at the time of the first visit.

    I arranged to bring in another company to verify the diagnoses and to provide another quote ... as the furnace stopped after the first company tech left the alligator clips connected this was not an option.

    I have requested quotes from other companies for a replacement. I was just trying to figure out if I could get the furnace running for the short term while I had a chance to consider my options for a few days.

  5. #5
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    Default Re: force air gas furnace problems

    Hi canuk,

    Thank you for your reply.

    Quote Originally Posted by canuk View Post
    foobar64 ....


    The first question is do you have an electronic thermostat?

    Next would be ... when you say the blowers are running constantly ... both or just the Induced Draft Blower?

    Did the second technician jump the negative pressure switch?

    You can try this yourself by disconnecting the two wires from that switch and touching them together while the IDB is running and there is a call for heat.

    Check to see if the rubber hose between the IDB and the vacuum switch is disconnected or has a split.

    In my opinion if there is a problem with the furnace not operating ... that company should be footing the bill for getting it operating back to the way it was before.

    Hopefully this helps.
    Your comments are very helpful!

    I do have an electronic thermostat. The fans run even when it is turned off. And the wires from the thermostat are disconnected from the control board.

    Both blowers are running (circulating fan and exhaust fan).

    I don't think the 2nd tech jumped anything. He did check the voltage between the board and the switch which allows the gas into the burner.

    I checked and I don't see a rubber hose. The is a metal one and it looks okay.

    I am having trouble trying to convince the owner of the company that he needs to fix the furnace because he feels that I will need to replace the furnace eventually. So I was just looking to see if I could provide him with an argument as to why his tech did break the furnace. You comments have helped with this.

  6. #6
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    Default Re: force air gas furnace problems

    foobar64..... good for you in having second or third opinions regarding the condition of your furnace.

    I totally agree it's unsafe to operate the furnace that has a leaky heat exchanger.

    There are those companies that will see a 13 year old furnace and try to sell you a new one and they will claim the heat exchanger is gone to shock you into replacing the furnace. That's not to say your furnace isn't in need but your doing the right thing with other opinions.

    Good luck.

  7. #7
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    Default Re: force air gas furnace problems

    Hi ****hiller,

    Thank you for your reply.

    Quote Originally Posted by ****hiller View Post
    foobar,

    Gotta say that if the HE is indeed shot......any potential problems caused by the left-behind alligator-jumper wire seems kinda moot at this point.....unless perhaps you're thinking about replacing the HE instead of the whole furnace. Not sure if that would really be cost-efficient in the long run if this furnace is already 13 years old.
    I agree that a new furnace is probably where I am going to end up with this. It is frustrating that I am having to a make a decision so quickly as it is November and I live in MA.

  8. #8
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    Default Re: force air gas furnace problems

    foobar,

    I understand your frustration. The problem with furnaces is that never go sour on us when we don't need 'em. That because we only run 'em when they're needed to prevent shivering.

    And yes, I totally agree that unless the furnace was flagged, they should have left it functional. It's a little difficult to determine from the symptoms just exactly why it isn't firing now. Fact is that there's numerous different types of controls on furnaces these days, some of which are unique to the manufacturer.........and may only have been used for a year or three or five. If we had some pictures of yours we might be able to put together a fault-tree to help you get it up and running, but from the sounds of things you have someone else coming over and hopefully they'll get the job done.

    If the HE has a crack in it, it can likely be plugged/patched for the short term, giving you more opportunity to shop around. However, please make CERTAIN that you have a CO detector in place if you take the patch route.

    It may be that the first tech company IS trying to hood-wink you about the need of a new unit. That's something that just can't be judged with certainty from here. If there is no crack in the HE which confirms some "hood-winking", then needless to say, I'd sure avoid them in the future. I'm sure you will, also.
    Last edited by goldhiller; 11-05-2007 at 09:44 AM.

  9. #9
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    Default Re: force air gas furnace problems

    Service Bulletin SVB01-6 from Armstrong for Ultra 80 SX (but you likely would have an older model smart valve):

    http://www.eccohtg.com/links/Service...%20SVB01-6.htm
    DW ....Nice find

  10. #10
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    Nov 2007
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    5

    Default Re: force air gas furnace problems

    Hi ****hiller, DwarfWytch, and canuk,

    I appreciate your technical help and support with my furnace problem. It helps me to understand what is going on. I am not planning on fixing the furnace ... by understanding, I figure I can be a better customer when talking with the technician who is working on the furnace. So that I learn what is important and what is not.

    The service bulletin DwarfWytch found is especially helpful here. I promise to not to try and fix it my self.

    And to ****hiller I have a CO detector in my basement and through out the house.

    Just an update, I found out the HE is still under a 20 year warranty. I found the company which actually installed the furnace . They are not local ... which is why I did not realize they were still around. So I have an appointment to have one of there techs to come out an diagnose the problem.

    I also have some good quotes for a new furnace should I need to follow that option.

    Thank you all again! You have been great!

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