Furnace 20 year old trane xl80. Flame lights then goes out after 5 seconds. Turn power off and works fine for about 5 hours then have to repeat. Replaced flame sensor, still problem. Model# TUD090A936A0

Dale Koehn

• 88 Answers
• Posted on Jan 27, 2009

SOURCE: Where is flame sensor on my old oil furnace?

Thanks for your question,
The flame sensor eye is located just under the transformer, it is looking straight down the burner assembly to where the burner chamber is at, you will have to remove the entire assembly to get to it, first make sure the power is off, remove the transformer, then remove the entire burner assembly from the furnace cabinet, once removed you can see the flame sensor window, use a clean oil free cloth to clean it, it would probably be a good idea while you have it out to replace the burner nozzle, as over time they will clog, I hope this helps you fix your oil burner, let us know and rate this please, thanks again,
mr.grzz

SOURCE: pilot light will not light

Sounds like you may need a new electronic control module. This is a rectangular shaped plastic box that has wires coming out of it. This is what tells the pilot to light on these older furnaces.

SOURCE: My furnace shuts off sometimes after the first 20-30 seconds.

The two most common reasons I have found for this are listed below. You have already addressed the third one.

1) Grounding issue. This can be difficult to find but easy to diagnose. Try using a volt meter or even just a piece of wire. Touch one end to an unpainted surface of the interior furnace cabinet and the other end to the sheet metal plenum or other ground. If the symptoms go away then you have diagnosed the problem and need to find the faulty ground.

2) Pressure in the flu. Check to make sure that the flu vent pipe is not clogged or even partially filled with debris. The small rubber hose that connects to the switch from the inducer blower motor may be clogged. Also check the orifice on the inducer motor side. You can clear this with a paper clip. Water (condensation) in the inducer motor housing or pressure switch can cause a failure too. Rarely is the pressure switch itself bad. This usually will only happen if it has been physically damaged or soaked. Best of luck.

SOURCE: flame rollout sensor keeps tripping

The flame rollout sensor is a rather important safety feature that ideally only trips when there's an overtemperture outside of the combustion chamber. I'd encourage you to get a better quality tech in ASAP to check for a cracked heat exchanger, gas overpressure, restricted airflow (changed the filter lately?), maybe a blocked condensate drain if this is a high efficiency furnace. If the sensor was replaced and it's still tripping, you've got a potentially dangerous overheating issue that you don't want to try to bypass.

SOURCE: furnace flame goes low fan stays on

if the gas pressure is good on inlet and outlet of valve u might wanna chk the burner trays and manifold for flakes, dirt, spider webs ect... once u kno the passages are clear from obstruction you can focus on the mechanical. (sounds like gas valve may be getting weak and not able to open fully)