Intermittent Furnace Start-up Problem

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Old 01-11-18, 01:42 PM
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Angry Intermittent Furnace Start-up Problem

I have a carrier PAV58 updraft gas furnace and it is controlled by a Honeywell Wifi Thermostat RTH6500WF. The furnace is 18 years old and the thermostat is 2 years old. There are times when the thermostat will sense temperature drop and request the furnace to start up and the furnace does not start. Then, some time later after the temp has fallen another 4-6 degrees, the furnace will start and run fine. Last year I thought that the draft inducer motor may be the problem because it was drawing quite a high current at startup. So I replaced it. Then it seemed to run fine for the rest of the season.
This year, when we got into a very cold two weeks it started doing it again. I also discovered that when the temp was below threshold and the thermostat said "heat on" on the screen, if I went to the furnace and turned off all power to the system for about 10-15 seconds, when I turned on the power it would cycle normally. I had called a tech in to check it and all he wanted to do was sell me a new furnace for full list.

So does anybody have any experience with this kind of problem. could it be something as simple as a dysfunctional relay. It always will eventually start-up after some time but this is quite annoying as my wife complains when she feels the cold of a 5-6 degree drop in the house. What should I do next??
 
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Old 01-11-18, 04:40 PM
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Welcome to the forums.


So does anybody have any experience with this kind of problem.
There are hundreds of threads with the same exact problem you have.

It's nice to have the full model number as there are several series in the 58PAV group. You can find it on an ID tag on the side wall inside near the burner.

The group manual shows a sight glass in the blower door which means your furnace has a control board with a diagnostic LED on it. You may have to reset power to clear a default LED flash code. The codes are listed on the back of the blower door. Keep an eye on the codes and let us know what you see.
 
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Old 01-12-18, 05:19 PM
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Pete, I will get the full model number and will try to get the diagnostic code the next time it decides to malfunction. Lou
 
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Old 01-19-18, 06:38 AM
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Could it be a shutdown issue?

pete, the full model number is 58PAV07016112.
So, after about 5 days of normal operation, it has now been quite regularly, malfunctioning. About 50% of the time. It sets a 14 code. And some time later, it resets itself and starts normally. Just as before, whenever I kill power to the system, it resets, starts normally and runs normally. And it shuts down in normal sequence.
When the thermostat requests heat and it does not start, I do not hear the draft inducer start so it seems that it does not initiate a start-up at all. Could this be because something did not properly shut off on the last power down sequence that is causing the next start request to be aborted?? If so, what could it be? What sensors could get stuck? Or is this a control board malfunction?
 
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