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Old 03-03-2013, 02:50 PM   #1
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I have a propane gas furnace that runs just fine 90% of the time. The problem is that the furnace goes into a default mode with the diagnostic code of rollout switch before the burner has enough time to heat up the switches and cause them to open. It does not happen all the time but when it does the fan runs at high speed and the diagnostic light blinks 5 times which implies that a rollout is the culprit. Only the furnace burner just barely gets started into it's heating cycle. There are 5 rollout switches on the heat exchanger and on the squirrel cage and none of them have needed to be reset. What else could this default be telling me to look at ? Could the rollouts that are connected in series somehow be shorting out or becoming disconnected and causing the default?




Dave in the hollow

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Old 03-03-2013, 03:50 PM   #2
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One of them could have carbonned contacts, and cause the error. Of course, tis often means that it has been getting hotter then it should, and there is a problem somewhere causing it.

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Old 03-03-2013, 06:00 PM   #3
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Hey Beenthere,

Thank you for responding so soon. Do you mean the rollout switch could be carbonized or mabe the contacts somewhere else? Is there someway to test them because I have bypassed each switch with alligator clip to eliminate one switch at a time and it still went to default.

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Old 03-03-2013, 06:05 PM   #4
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The contacts in the roll out switch. You can ohm them and see if they show resistance.
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Old 03-03-2013, 08:22 PM   #5
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Been there

I was wondering why the furnace would run most of the time if the switch was carbonized. Those switches are fairly cheap should I just buy new ones and eliminate that as the cause and if that does not fix it any thoughts on what to try next?

Dave in the hollow
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Old 03-03-2013, 09:45 PM   #6
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Maybe you are getting a backdraft. You are in the Hollow, right?
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Old 03-03-2013, 09:59 PM   #7
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Quote:
Originally Posted by hayeshollow View Post
Been there

I was wondering why the furnace would run most of the time if the switch was carbonized. Those switches are fairly cheap should I just buy new ones and eliminate that as the cause and if that does not fix it any thoughts on what to try next?

Dave in the hollow
Better to test them. then if one is showing high ohms. You know to look for a problem, instead of just covering up the problem until it gets worse down the road.
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Old 03-06-2013, 09:52 PM   #8
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Hey Beenthere,

I was wondering if I want to test the roll out switches do I need to take the switches out or can I test them on the furnace? Basically I just want to test the switch for resistance? What if they seem to be all right could there be something else causing the default? I'm pretty sure that it's not a backdraft since it really only happens right before the burner kicks on. Thanks for the input Jagans but since I'm in the hollow the wind blows right over us and causes a updraft

Dave in the hollow
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Old 03-07-2013, 05:19 AM   #9
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You can remove the wires and ohm them in place. Sometimes works better if you do a voltage test across them while the unit is running, or trying to run.
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Old 03-10-2013, 09:22 AM   #10
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Hey Beenthere,

I have checked the rollout switches with a ohm meter and all of them showed no resistance but the furnace is still showing rollout defaut occasionally then it run just fine other times.Do you have any other test I can try to help me fiquire out what is the problem?

Dave in the hollow
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Old 03-10-2013, 11:44 AM   #11
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Could be a worn out molex connector on the board. Trane has a model or 2 that are know for that. Check out all connections on the board.
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Old 03-10-2013, 12:03 PM   #12
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Yep. you need to remove them and carefully look into the sockets and on the pins and see if one of them got pushed backwards out, use a magnifying glass. Not just on the board as there may be some in wiring harnesses from the board up to the gas valve, rollouts.

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