:eek: My attic furnace (Rheem Classic 90 Plus) ignites and then flames out after only a few seconds. I have found water pooled in the pan below the furnace on a few occasions. I have found similar problems & solutions online, but the lingo is a little over my head. I need somebody to describe what I am looking at.

If the circuit board has a diagnostic LED, observe it and check the service label for an explanation. What you describe is consistent with what happens as a result of a dirty flame sensor.

Which is the flame sensor?

Look for a small, ceramic-insulated steel rod, mounted on the burner assembly, with a single wire attached. Don't confuse the ignitor for this (2 wires). Taking it out and cleaning it with abrasive cloth or steel wool restores its sensitivity to flame current. HVAC1000, WE HAVE ANOTHER PHOTO OP!:p

A little late but here it is.

If your condensate drain on the furnace is restricted the pressure switch will open and shut the furnace down. Check for a restricted drain line, that may be the reason why you are seeing water around the furnace. The rubber lines from the collector box inside the furnace going to the condensate trap have been known to deteriorate and come apart.

Best answer ever and all I needed to know is which was the ignitor and which was the sensor. Thanks

Thanks for the illustration!

They say not to use steel wool anymore. I was advised by my service shop to only use a damp rag and rub hard to clean off the flame sensor and it has been working ever since.