trane blu108e936b1

[jimsin630]

It's cold here just west of chicago, and i've got a problem that started yesterday

pilot light lights IMMEADIATELY, furnace runs, then after a few minutes, gas shuts off, including pilot light, has normal operation until this happens, but doesn't get to full temp

have replaced themal sensor even though pilot light was staying lit.

am leaning towards gas controller because when this happens, there is a click like a relay/solenoid going of, but don't feel it in controller

[ACtechGUY]

It sounds like the furnace may be over heating and shutting down due to high temps. Take a temp reading in the supply duct . most furnaces are supposed to raise the air temp between 40 and 60 degrees (the exact rating is on the label. ) If you get a really high reading (like 140 or 150 ) you have an airflow problem.

Check for dirty filters and a dirty evaporator coil. make sure all supply air grills are open . Any airflow restriction can cause a furnace to overheat.

[jimsin630]

thanks for tip, have laser thermometer at work ( mechanic), will check today

[ACtechGUY]

A probe type thermometer will be more appropriate. You will need to make a small hole in the supply duct very close to the furnace and take a temperature from that point.

[jimsin630]

thanks again, you were correct. have 2 temp probes, 1 duct work and 1 redundant. had to call repairman due to temps expected

the redundant is kicking out, partially due to restricted flow. have to find a new sensor, but in meantime is by passed, still have primary in place which is working

thanks again, jim

[ACtechGUY]

Another thought.... If you have a washable filter, try without the filter. Sometimes(OFTEN) washable filters get restricted .