Limit switch question

Questions about repairs and parts for Coleman furnaces, air conditioners and heat pumps for manufactured homes. Click here for Coleman parts.

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Joined: Sun Nov 03, 2019 2:22 pm

Hello everyone. This is my first post- Thanks for added me.

I have a 22 year old Coleman DGAT075BDD furnace. We do not have air conditioning just propane heat.

One day this past summer I heard the blower come on and switch off again. it started to repeat this cycle of on and off. The system was off at the wall thermostat and kept doing this until I turned the furnace off at the system switch on top of the control board enclosure.

I kind of forgot about but now that autumn is beginning I need to get this issue worked out. Today I disconnected the wiring to two upper limit switches and to the fan limit switch and checked the continuity to each. All three were closed. I next turned the system switch back on and I have a solid green LED with no on and off cycling of the blower. There was no noticeable corrosion on any of the spade connectors on the limit switches.I did not actually run the furnace today, I just turned the power switch on.

1. When these limit switches fail is it sometimes intermittent?

2. Can they fail in such a way that the perimeters shift so that the ambient temperature inside the furnace on a hot summer day might be enough to trigger a problem but when it cools off in the fall it may test OK?

It's not that they're very expensive so I could simply replace them all.

I did have a leak around the stack early last winter which dripped down and blew the control panel. I replaced it and the furnace worked fine. There is a little rust around one of the upper limit switches so i was kind of expecting that one to check out bad but it didn't.

Thanks again. I appreciate any knowledge that can be passed on to me.
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