fan limit switch

Problems related to residential installations.

fan limit switch

Postby travjudd » Wed Dec 04, 2013 1:17 pm

I have a 1990 ICP gas furnace model# NUGE100BG01 with honeywell controls. The furnace comes on fine but after 5 minutes the flame goes out due to the fan limit switch rising above 200 degrees. I have a new filter and opened all of the supply vents. I checked the temperature at the first supply vent and it was a consistent 122 degrees. I pulled out the temp probe on the limit switch and immersed it into boiling water to gauge if it is accurately depicting a temperature. It was actually lower than 212 degrees. I put a 4" temperature probe in the spot where the limit switch was and it only registered a 141 degrees. I did some research and some people with the same problem stated that it was from having to big of a furnace to their house. Can these limit switches temperature probes go bad or is there something that be causing the probe to actual see that high of a temperature.
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