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    #1

    Furnace problems

    Ok the power is back on but I can't get my furnace to lite off. Its a natural gas unit with a standing pilot light. The pilot light never went off but since I couldn't get the unit to kick I shut it all the way down and started from square one. I got the pilot burning again but it stll wouldn't lite off the main burner. Next the thermostat went blank. In the past years here we have had to replace the thermostat a few times. I bought a new one yesterday but haven't installed it yet. Its only a simple two wire setup. here is my dumb question.... If I short the two wires at the thermostat as a test shouldn't this cause the furnace to kick in? Can I check at the thermostat with my VOM for voltage without blowing out my furnace control board??? My friend Chuck could fix this but I'd rather do it myself. It has to be something simple wrong here.
    "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
    Mark Twain

    "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
    John Paul Jones

    There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
    Rod Serling
    Tags: None
    #2
    Re: Furnace problems

    Yes, shorting the wires should make the furnace come on.
    If you're testing at the thermostat, it should be 24vac ( I think, maybe 48, I'm a bit foggy at the moment)

    Is there a switch near the furnace that may have gotten turned off?
    We have one on the wall by a shelf, and sometimes manage to accidentally turn it off.
    36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

    Comment

      #3
      Re: Furnace problems

      shorting the 2 wires should turn it on.control voltage is 24vac.
      thermostat if its a digital one runs from the 24v or batteries.the suggestion to check the switch or breaker is a good one.

      Comment

        #4
        Re: Furnace problems

        The thermocouple sits in the pilot light flame. It's the fine piece of tubing leading to the bracket that holds the pilot and runs back to the main gas valve.

        It can fail one of 2 ways:
        It prevent the pilot light from staying lit. (yours is working this far)
        It can prevent the main gas valve from opening.

        If you cross the 2 thermostat wires, you should hear the gas valve -clunk- and you should see the pilot light flame get bigger so it hits the burner. Shortly after the pilot flame gets bigger, the gas valve will move again and open to supply the burners with gas.

        Other possibilities are a failed or stuck lower and upper fan temperature limit switches. Low is usually set from 100-110°F and high is around 175°F. This is adjustable. Pay attention if you need to change it to NOT ROTATE the dial. HOLD the dial and move the sliders.

        Then there is a high temp cutout that prevents the whole unit from overheating (usually not adjustable).

        Report findings.

        Toast
        veritas odium parit

        Comment

          #5
          Re: Furnace problems

          The furnace has a breaker in our main pannel. It also has two off switches. One is the Red plated emergency shutoff in the hallway. The other is located near the furnace both of these and the furnace breaker are switched on. I checked the 24 volt side in the furnace and at the thermostat and got zero volts at both places. My brother is on his way over to fix this thing or at least try to. Me !
          "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
          Mark Twain

          "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
          John Paul Jones

          There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
          Rod Serling

          Comment

            #6
            Re: Furnace problems

            Toasty I saved that for my brother to look at when he gets here.
            "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
            Mark Twain

            "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
            John Paul Jones

            There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
            Rod Serling

            Comment

              #7
              Re: Furnace problems

              if this is a furnace that heats water in a coil to feed radiators & sinks then check the pressure safety switch on the incoming water supply.

              Comment

                #8
                Re: Furnace problems

                AC scale on meter, yes?

                Transformer should be humming(lightly) and a little warm.

                If switches are on, and its cold, then it sounds like the transformer is toast. Quickie (cheap) fix.



                Toast
                veritas odium parit

                Comment

                  #9
                  Re: Furnace problems

                  We have 120 vac comming into the furnace. The 24 vac out of the little transformer is at 0. We are calling a furnace repairman we know to fix it. Sorry my report isn't detailed Toasty. I'm tired and done thinking about the thing for today. I have electric heaters in place. We will be fine until its fixed.
                  "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
                  Mark Twain

                  "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
                  John Paul Jones

                  There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
                  Rod Serling

                  Comment

                    #10
                    Re: Furnace problems

                    If your furnace has a standing pilot it's probably as ancient as mine.

                    Did you hold the button on the thermocouple shutoff gas valve?

                    After lighting the pilot trace the thermocouple tube to the thermocouple gas shut off hold the button all the way down for a few seconds then release.

                    The tiny voltage induced from the heat to the thermocouple holds the gas valve open this prevents the burner from from flooding the house with gas should the pilot go out.

                    If the transformer isn't getting power check the emergency shutoff switch for the furnace there should be a red switch plate that says burner on it. I believe it's code for all furnaces to have one.
                    Last edited by Krankshaft; 11-11-2010, 01:05 PM.
                    Elements of the past and the future combining to make something not quite as good as either.

                    Comment

                      #11
                      Re: Furnace problems

                      I held the button in for a full 60 seconds like the destructions said to.
                      "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
                      Mark Twain

                      "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
                      John Paul Jones

                      There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
                      Rod Serling

                      Comment

                        #12
                        Re: Furnace problems

                        Well then it sounds like a dead transformer or a wiring problem to it.

                        Does your gas solenoid have a test knob on it? Mine does.

                        You can turn it and it will allow you to open the gas valve manaually to see if the thermocouple is working release the knob and it will close. If the burner fires up the thermocouples fine and it's an electrical problem.
                        Elements of the past and the future combining to make something not quite as good as either.

                        Comment

                          #13
                          Re: Furnace problems

                          I'm going with it being and electrical issue because I have no volts going to the thermostat from the transformer. There is A/C power going to it.
                          "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
                          Mark Twain

                          "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
                          John Paul Jones

                          There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
                          Rod Serling

                          Comment

                            #14
                            Re: Furnace problems

                            Disconnect the secondary side of the transformer and see if you have 24-27 volts AC on the secondary. If 0 volts, replace the transformer. If you have 24-27 volts, look for a shorted component.
                            Stupidity should be a crime, especially for drivers. I have NO patience for them.

                            Comment

                              #15
                              Re: Furnace problems

                              I took a real close look at the terminals on the transformer and I think I can see what caused the problem. One of the thermostat wires shorted to another terminal on the transformer. My furnace fixing friend John is going to take care of it in the morning. Since I think it got shorted I'm going to hang the new thermostat I have here too. Hope nothing expensive got fried.
                              "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
                              Mark Twain

                              "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
                              John Paul Jones

                              There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
                              Rod Serling

                              Comment

                                #16
                                Re: Furnace problems

                                Success?
                                veritas odium parit

                                Comment

                                  #17
                                  Re: Furnace problems

                                  burnt up the transformer no doubt.too bad you are nor close by.i could grab one out of spare parts in about 30 seconds.replace it yourself and save the call.hell radioshack has a 25.2vac 2 amp unit that will do.

                                  Comment

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