Furnace Problem Solved (Could be fire issue)

[zzvyb6]

I have a 20+ year old 95% FUE Comfortmaker which just started to act up. It heats the house, then goes into a 'lockout' mode in which the computer blinks continuously and the fan runs at full tilt. Book says to cycle the power. It starts and runs normal after that until things warm up. The blink code is supposed to mean 'flame sensed with no call for heat' which doesn't mean crap to me. All the other blinker codes indicates some real problem (pressure switch, grounded condensate, etc). Anyways, I pulled out the flame sense switch and cleaned it, no effect. Checked for water in the condensate trap (you MUST have some in there for it to work, but not excess), no effect, and then pulled out the heat limit switch. It was a bit charred and disintegrated when I softly removed it. New one was $15. from a parts guy down the street but new ones on internet can be $150. Put the new limit switch in and it fired right up no further problems.

Furnace part guy told me that a lot of the new super allergen filters are causing furnace problems because they restrict the airflow too much causing an overheat situation. That can tax the limit switch & surrounding material properties. I changed the filter, too, BTW.

Just thought I'd pass on this information. The charring on the limit switch and wiring made me concerned about fire possibilities.

That's all folks !!

 

[grsthegreat]

I have a 20+ year old 95% FUE Comfortmaker which just started to act up. It heats the house, then goes into a 'lockout' mode in which the computer blinks continuously and the fan runs at full tilt. Book says to cycle the power. It starts and runs normal after that until things warm up. The blink code is supposed to mean 'flame sensed with no call for heat' which doesn't mean crap to me. All the other blinker codes indicates some real problem (pressure switch, grounded condensate, etc). Anyways, I pulled out the flame sense switch and cleaned it, no effect. Checked for water in the condensate trap (you MUST have some in there for it to work, but not excess), no effect, and then pulled out the heat limit switch. It was a bit charred and disintegrated when I softly removed it. New one was $15. from a parts guy down the street but new ones on internet can be $150. Put the new limit switch in and it fired right up no further problems.

Furnace part guy told me that a lot of the new super allergen filters are causing furnace problems because they restrict the airflow too much causing an overheat situation. That can tax the limit switch & surrounding material properties. I changed the filter, too, BTW.

Just thought I'd pass on this information. The charring on the limit switch and wiring made me concerned about fire possibilities.

That's all folks !!

flame sense with no call for heat means the heat sensor is detecting heat even though the heater isnt operating. ie: defective flame sensor (heat sensor) . you got it fixed by trial and error A++++++

i had a similar thing happen to my unit about 2 years ago. got my parts thru ebay

 

[kenmac]

If your duct work wasn't designed to use restrictive filters you shouldn't use them. They will restrict air flow which affects heat & a/c. You should have gotten an open limit code

 

[zzvyb6]

I would have expected '4 flashes' (Open Limit code), as the ops manual says, but clearly the new limit switch did the job. And, the 'flame sense' transducer was fine. Cleaned it off a tad, but otherwise it had no effect on the problem.

 

[kenmac]

I would have expected '4 flashes' (Open Limit code), as the ops manual says, but clearly the new limit switch did the job. And, the 'flame sense' transducer was fine. Cleaned it off a tad, but otherwise it had no effect on the problem.

I never go by the led. New techs are hard to train because of LED'S. They go by the flashing light & replace parts that still don't solve the problem.. I use the old fashon method. Volt meter

 

[Sigarms]

I never go by the led. New techs are hard to train because of LED'S. They go by the flashing light & replace parts that still don't solve the problem.. I use the old fashon method. Volt meter

For the most part, we always seem to be on the same page LOL

I call diagnostic boards idiot lights. Replace pressure switch, replace inducer motor, replace gas valve, replace pilot assembly, replace board. It's got to be one of them!

You'd be amazed at how many times you ask a tech if they have a dedicated ground coming into the furnace and they say "I think so, why would it matter?" (please see above about replacing parts). Also amazed when you ask what the gas pressure is coming in and going out and the response is "don't know, but the burners don't look like they're firing right".

Furnace part guy told me that a lot of the new super allergen filters are causing furnace problems because they restrict the airflow too much causing an overheat situation.

Ask your furnace guy about static pressure drop.

If your duct work wasn't designed to use restrictive filters you shouldn't use them.

You mean to say people actually design ductwork?:laughing:

 

[kenmac]

For the most part, we always seem to be on the same page LOL
You'd be amazed at how many times you ask a tech if they have a dedicated ground coming into the furnace

Maybe because we learned to trouble shoot the old fashion way ( B-4 the idiot light)


Ground ? I've heard... The unit should will b good enough ground??:laughing: