Inducer repeats cycle while furnace otherwise runs normally

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Old 12-21-13, 07:42 PM
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Inducer repeats cycle while furnace otherwise runs normally

Trane XL90 now ten years old runs on propane. Recently, from the sound of it, the inducer runs, the furnace lights and runs, but while the furnace runs through a normal cycle, the inducer seems to restart and run once and even twice again while the furnace main blower is running and heating the house. We are thankful of the heat, but the sound is disconcerting as the inducer runs repeatedly. I guess the inducer has a sensor which tells it that it has succeeded and that this sensor is dysfunctional, so the inducer is oblivious to the fact that the burners are lit and so it goes on repeating its cycle. Question: what is the part that is supposed to tell the inducer that it has succeeded and that another inducer cycle is not required? Thank you!
 
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Old 12-21-13, 08:05 PM
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Your furnace should display a blinking trouble code that will help in diagnosing this problem.
 
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Old 12-21-13, 09:22 PM
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Yeah. I guessed wrong about the inducer. It must be obvious that I am trying to understand this thing just by listening and watching it work. Twice I had a professional out years ago and for all that money that I couldn't afford to pay, they stood there on the phone with someone else describing this and that and then told me I need a $600 kit (and God knows how much for labor) that just replaced almost everything. In other words, they didn't know what in particular was wrong, either. I've tinkered with it myself ever since, cleaning drain lines, replacing ignitors, disassembling and cleaning the burners, replacing a burned ground wire, etc. I've kept it alive for the past five years this way. It's just that recently, a new sound/behavior has come about and I am just guessing at the cause. This system has always had a big problem with water, too. The inducer drives a small blower that sounds like it's got water inside. I just cleaned and drained those lines again tonight. I opened the top panel and sat through a full cycle. It ran normally this time. What it did to make me come here was start and run normally then suddenly stop and then restart. It's intermittent. It often runs normally all the way through a cycle. I've owned the home for six years and it has been unreliable all six years. It was newly installed four years before we bought the house. Assuming it worked for the previous owner, it may have given four years of trouble free operation. Very unimpressive.
 
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Old 12-21-13, 09:40 PM
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Oliver..... Houston mentioned checking for a trouble code. Have you done that ?

It sounds like one of two problems....one is the heat exchanger is getting too hot causing the burner to shut down until it cools and then it will relight. The blower will stay running the entire time.

or the pressure switch, due to an exhaust issue, is shutting down the burner.

Either way... without a code.... we're guessing.
 
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Old 12-22-13, 04:36 PM
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My first step would be to hook up a meter to the inducer motor leads to verify that it is either being shutdown due to the power being cut off from the source or it continues to receive power and is shutting off on internal overload and restarting after it cools off. After determining that we can move to the next step.
Your inducer motor has a safety pressure switch and if the inducer fan stops running regardless of the reason then the gas valve MUST shutdown immediately. You mentioned that the blower fan still runs but does the burner shutoff???
 
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