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Gas Fired Forced Air HVAC Problem

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  • #16
    Re: Gas Fired Forced Air HVAC Problem

    Originally posted by plumberscrack View Post
    Plenum switch is not same as pressure switch. It's the limit switch that controls the air temp in the duct.

    You can try jumping the pressure switch BUT you probably have to do it AFTER the inducer powers on. Once it shuts off you have to break the connection again before it will fire again. Does this makes sense?
    It's set up this way so in case the pressure switch sticks in the closed position.

    I'm sure you have a manometer. Check gas pressure against specs on unit.
    I will check the gas pressure but all the gas valves have been replaced and the HVAC guy says all that checks out. BUT I will check myself this weekend ...yes I have a manometer....I can handle all the gas line checks.

    Ok now what would jumping the pressure switch tell me? The unit does fire some times on its own...just somtimes it will not. The girl said it seems to not want to turn back on if the unit doesn;t get used for a while.....XAMPLE....Say the temp in the house is 72 degrees and its time for her to go to sleep.....so she turns the unit down from 72 to about 65 degrees.....and when she wakes up at 6 am its freezing in there. This morning the units inducer came on...but it never fired.......then about 3 hours later the unit fired up and warmed the house.

    I'm hoping for somthing i can check with a multimeter...or jumping a switch permanenlty for a few days to see if thats the bad part....There must be a way to check units without being a parts changer.

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    • #17
      Re: Gas Fired Forced Air HVAC Problem

      Originally posted by TheMaster View Post
      I will check the gas pressure but all the gas valves have been replaced and the HVAC guy says all that checks out. BUT I will check myself this weekend ...yes I have a manometer....I can handle all the gas line checks.

      Ok now what would jumping the pressure switch tell me? The unit does fire some times on its own...just somtimes it will not. The girl said it seems to not want to turn back on if the unit doesn;t get used for a while.....XAMPLE....Say the temp in the house is 72 degrees and its time for her to go to sleep.....so she turns the unit down from 72 to about 65 degrees.....and when she wakes up at 6 am its freezing in there. This morning the units inducer came on...but it never fired.......then about 3 hours later the unit fired up and warmed the house.

      I'm hoping for somthing i can check with a multimeter...or jumping a switch permanenlty for a few days to see if thats the bad part....There must be a way to check units without being a parts changer.

      Don't jump ANY switches permanently. Lawsuit written all over that move.

      Comment


      • #18
        Re: Gas Fired Forced Air HVAC Problem

        These kind of things are tough to troubleshoot. If it doesn't fail while the tech is there staring at it then it's just becomes a guessing game as to what it could be. He chose the control board and gas valve. Two likely suspects. Maybe they WERE bad, maybe not. I here and not there.

        A board from that era will go into lockout mode and not give you an indication of what went wrong. No blinking LED to clue you in. Not familiar with that particular board so I can't say what it does or doesn't do when it has a system problem.

        Does the inducer continue to run the whole time when it's not firing? Then all by itself it comes on? That tells me the inducer isn't coming up to speed or pressure switch is weak or the chimney has a pelican nest on top.

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        • #19
          Re: Gas Fired Forced Air HVAC Problem

          I think this HVAC guy should call it a career.

          Comment


          • #20
            Re: Gas Fired Forced Air HVAC Problem

            Originally posted by James P View Post
            Don't jump ANY switches permanently. Lawsuit written all over that move.
            When I say permanent I mean for few days so we can make sure thats the issue....I agree with you but in this case I wouldn't be sued if anything happend. Its my parents house.

            Originally posted by plumberscrack View Post
            These kind of things are tough to troubleshoot. If it doesn't fail while the tech is there staring at it then it's just becomes a guessing game as to what it could be. He chose the control board and gas valve. Two likely suspects. Maybe they WERE bad, maybe not. I here and not there.

            A board from that era will go into lockout mode and not give you an indication of what went wrong. No blinking LED to clue you in. Not familiar with that particular board so I can't say what it does or doesn't do when it has a system problem.

            Does the inducer continue to run the whole time when it's not firing? Then all by itself it comes on? That tells me the inducer isn't coming up to speed or pressure switch is weak or the chimney has a pelican nest on top.
            I totally agree and understand that some things you cant for sure say its this or its that part causing the trouble. I still think the guys are total idiots...and they are fairly new to this company that has serviced the unit on and off for 5 or 6 years.

            The HVAC guys says its hard to troubleshoot the unit because when you remove the front panel it turns the unit off....WTF I know you can jump that switch or tape it down...WTF. Guys an idiot.

            I will check for nests and suspect the pressure switch....if they are still having trouble...I will go ahead and buy the pressure switch and replace it. Hell I can guess and start changing parts hell of alot cheaper than those clowns can.

            Originally posted by Flux View Post
            I think this HVAC guy should call it a career.
            I'm going to call them after this gets repaired and let them know what was wrong with it. They are not coming back. If they get smart I'ma tell'um to get f'd. and do what I do.

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            • #21
              Re: Gas Fired Forced Air HVAC Problem

              I am currently dealing with a 15 year old Bryant Plus 80, same as the Carrier brand. Did you examine the heat exchanger, I did and mine is cracked. I wish someone would have told me this $300 ago. Back in the day had a problem with the steel in these. I would check his before anymore money is wasted.

              Also, the circut boards had an issue hk42f2011 was the number. I believe mine is bad, but the solution is a new furnace after I learned the heat exchanger is bad. They are on warranty, but about $500 to change them.

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              • #22
                Re: Gas Fired Forced Air HVAC Problem

                Originally posted by NorthernIllinoisPlumber View Post
                I am currently dealing with a 15 year old Bryant Plus 80, same as the Carrier brand. Did you examine the heat exchanger, I did and mine is cracked. I wish someone would have told me this $300 ago. Back in the day had a problem with the steel in these. I would check his before anymore money is wasted.

                Also, the circut boards had an issue hk42f2011 was the number. I believe mine is bad, but the solution is a new furnace after I learned the heat exchanger is bad. They are on warranty, but about $500 to change them.
                This heater is ran about 3-4 months out of the year...with lows in the 40's usually. Heaters just dont get heavy use here. less use = less expansion/contraction and condensation.

                Comment


                • #23
                  Re: Gas Fired Forced Air HVAC Problem

                  Thanks to all who have given me things to check this weekend or in the future if the issue persists. I have done some reading on how the system works in general. The sequence of operation and how to test various componets with a test meter. I think with a manomter,test meter and some help from you guys and what I can find reading on the web I will be able to repair it.

                  Comment


                  • #24
                    Re: Gas Fired Forced Air HVAC Problem

                    Originally posted by TheMaster View Post
                    I will check the gas pressure but all the gas valves have been replaced and the HVAC guy says all that checks out. BUT I will check myself this weekend ...yes I have a manometer....I can handle all the gas line checks.

                    Ok now what would jumping the pressure switch tell me? The unit does fire some times on its own...just somtimes it will not. The girl said it seems to not want to turn back on if the unit doesn;t get used for a while.....XAMPLE....Say the temp in the house is 72 degrees and its time for her to go to sleep.....so she turns the unit down from 72 to about 65 degrees.....and when she wakes up at 6 am its freezing in there. This morning the units inducer came on...but it never fired.......then about 3 hours later the unit fired up and warmed the house.

                    I'm hoping for somthing i can check with a multimeter...or jumping a switch permanenlty for a few days to see if thats the bad part....There must be a way to check units without being a parts changer.
                    The furnace most likely has a 3hr. lockout after 3 trials for ignition. Sounds more and more like the flame sensor is the problem.

                    I have an 8 year old Bryant in my residence and the flame sensor fails to sense the flame every so often on the first try.. I need to clean or replace it, just to busy. You can check it with a micro ammeter or clean it with steel wool or just replace it. No more than they cost I usually replace them.

                    James

                    Comment


                    • #25
                      Re: Gas Fired Forced Air HVAC Problem

                      Make sure the combustion fan is kicking on. When they start to go, sometimes they run, sometimes they don't. Sounds like the HVAC guy is not sure what is really going on, and just guessing.
                      Will Rogers Plumbing
                      Moore, Oklahoma
                      (
                      405) 323-2852

                      "Your Solution for Any Sewer and Drain Cleaning Needs"

                      "We Unclog Drains That Others Can't"



                      www.willrogersplumbing.com
                      http://willrogersplumbing.com/?page_id=8

                      "Oklahoma's Favorite Plumbers!"

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                      • #26
                        Re: Gas Fired Forced Air HVAC Problem

                        Well, what happened? Find the problem?

                        Thanks.


                        J.C.

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                        • #27
                          Re: Gas Fired Forced Air HVAC Problem

                          My vote is Col. Mustard in the library with the flame rod...

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                          • #28
                            Re: Gas Fired Forced Air HVAC Problem

                            Originally posted by OkieBill View Post
                            My vote is Col. Mustard in the library with the flame rod...
                            Switch Library with attic and I think you have a winner there. hehe

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                            • #29
                              Re: Gas Fired Forced Air HVAC Problem

                              BUMP. breid...................

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                              • #30
                                Re: Gas Fired Forced Air HVAC Problem

                                The problem was/is intermittant......it warmed up before any real time passed after everything was done to it. We shall see this coming winter. God knows we dont need heat now.....it was around 115 yesterday with the heat index factor(humidity)

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