flame roll out switch

[Centurian]

I have a weathermaker 8000 gas furnace....I switched it on for the winter season a couple of days ago...before that I cleaned the flame sensor...I did notice that the sensor was a bit slack inside the porcelain body..but as it seemed to hold OK so I installed it The furnace has been working OK.. but I did notice it was switching off then coming on a short time later , then switching off at the correct temperature...the thermostat setting is 0.5 degrees fixed span..which means it comes on 0.5 degrees under the setting and off 0.5 degrees over the setting this morning I took notice and it did it again...the code was flashing ...LIMIT OR FLAME ROLLOUT SWITCH OPEN...it then came on again after about 3 minutes and all OK I also noticed it was switching off always at 0.3 degrees above the setting..then coming on and off again at the correct 0.5 degree setting I thought it may be the thermostat ..but if it was then the code would not flash so I figure it must be the furnace....could it be a faulty flame sensor..and why is it going off at precisely 0.3 degrees all the time instead of 0.5 degrees nothing is locking out..it goes off ..code flashes..then comes on and goes off at the correct temp thanks in advance

[HayZee518]

anticipator

what is your heat anticipator set at? should be equal to the current of the gas valve. one way a few degrees from the set point will extend or shorten the proportional band.

[Centurian]

flame roll out switch

Thanks Hazee an update....I changed out the programmable thermostat as it was under 3 year warranty...and all seemed Ok yesterday...but this morning when it came on it ran OK for awhile then cut out again and same symptom... code 33 was Limit or flame roll out switch.. I played around with it... and it was running normal and cutting out OK..so I'm at the conclusion the limit switch is weak and cutting out prematurely after it has been running for awhile... like first thing in the morning after being off all night...so I'm letting it run today and keep watch on it and if it shuts down again I will check the limit switch for continuity and see if it opened...I have 3 minutes to do this as it resets automatically ..which seems to fall into the fault category... thank again for all your help...if it is the limit switch I will let you know

[Centurian]

flame roll out switch

Problem solved...put my voltmeter across the limit switch contacts and ran the furnace ..which quit prematurely after awhile....voltmeter showed 24 volts which meant switch went open...replaced switch and tested this morning ..ran OK and switched off when it was supposed to...switch must have went weak

[Brian_Martin_Parma_Air]

sound normal

thermostats fluctuate a couple of degrees. .5 degrees in no issue