Trane XE Furnace Problem

[airplanejoe]

I have a furnace that has a hot surface igniter and will turn red and you can hear the gas valve open. The flames will only stay on for about 3-5 seconds and go out. This happens about 4-5 times and the fan will start. The only way I can possibly get the furnace to keep running without the flames going is set the thermostat below room temperature and bring it back up to a higher room temp. What could be wrong? The pressure switch works!

Help

Joe

[a46geo]

You are re-setting an electronic safety lock out when you do this.

You can do the same thing by turning the furnace switch off and then back on. Although the burner is lighting, a sensor is not detecting the flame. Either a loose connection, a weak sensor or a circuit board is most likley the problem.

[airplanejoe]

Can you jumper out the flame sensor for a short period to eliminate or prove that the problem is the sensor?

Joe

[johngrider]

I am having a somewhat similar problem with my XE-90. The purge pump will run for about 30 seconds, nothing happens, starts again about 15 seconds. Cycle repeats and repeats. Does maintain the selected temperature on the thermostat. It appears tha the vacuum is insufficient to activate the switch to trigger the igniter. I have reset the thermostat(HONEYWELL PROGRAMMABLE) and it has cycled normally. Does the pressure switch have a designed in bleed? It appears that it has. If I actuate it manually(mouth) all seems to work?

[johngrider]

Follow-up to my prfevious post on XE90. Have verified that all air vents and condensate draines are not clogged. Could only get heat occasionally without pinching off the vacuum line to the back side(away from furnace) of the pressure switch (SWT 1612 replacement is SWT 2523). Decided to plug this line with a golf tee and all seems to work properly. Holds temperature and recovers from 65* at night to 72* at 7:30 am programmed. Don't see any unsafe conditions by doing this but don't understand why it works. Talked to another member that has a XE-90 and he did the same thing and his is working also. He had a technician replaced this vacuum switch without any change in performance. Question is "WHY DOES IT WORK WITH THIS LINE PLUGGED AND WHAT DO I DO NEXT?? Any help and comments would be appreciated.

John