[Johnny B]

Anyone currently on to help with above furnace. Was shot cycling at a max run time of 4 mins. Changed limit switch and problem persisted. Pulled pleated merv 7 filter an ran filterless (contractor approved as test measure), ran for 13 mins straight until I manually shut it down (at thermostat). Put in mer 5 bare bones filter, manually shut it at 9 mins. House was hot now so didn't call for heat for a while. Cleaned flue run back to unit & vacuumed around unit back. All was fine until 12 last night. Locked out twice due to over cycle. 2 steady red flashes. Rand a few times blowing cold air. Cleaned what I thought were 2 flame sensors (little looped items in upper corners of gas supply bar, then is ran ok. Woke up to cold air again. Thoughts?

 

[roughneck]

What do you mean by over cycle?
1" pleated filters, especially the high MERV rated ones, can be very restrictive and cause issues.

 

[Johnny B]

Thank you so much for response. Meant unsuccessfully try to start normally too many times in a row.

 

[beenthere]

Could be a dirty A/C coil if you have central A/C.

 

[supers05]

Sounds like flame failure. How did you clean those"sensors?" One will be a spark electrode. If it looks like an M or W then you shouldn't touch it, as it's probably a HSI. (very brittle) Cleaning the sensor or sparker is best done with emery cloth, fine file, or steal wool. Clean until they are shinny, and make sure that the burner plates nearest to them are also clean.

Pictures would help.

Cheers!