Trane XE80 Intermittant lighting problem

[mike99]

I am working on a trane XE80 with an intermittant lighting problem. This is what I am seeing.

1. When I first turn on the thermostat after it's been off for a while everything lights off fine and the furnace will run for a while (like 1 - 1.5 hours) before it turns off before hitting the thermostat temperature.

2. Furnace waits a couple minutes before it restarts the ignition sequence.

3. Ignition sequence starts, gas valve opens (can hear the hiss), but the hot surface ignitor is clearly not glowing this time around and there is no ignition. Repeats two more times then locks out.

4. Turning the thermostat off and on to reset the lockout SOMETIMES fixes the problem temporarily.

Any thoughts to the problem?

[jumptrout51]

1. clean the flame sensor with steel wool.
2. when the re-light attempt fails check continuity through  all the rollout switches.(no continuity,no power to ignitor).
3.check ignitor for power,with a meter not visually.
4. check for a open vent stack limit switch.
5. if everything checks OK replace the ignitor.

[tgoods]

Since you're hearing the gas valve open, the control thinks the ignitor is glowing.  Check for 120vac to the ignitor.  I bet you have a cracked solder on the control board. Jiggle the plug where the ignitor connects to the board.  Resolder it or replace the board.

[handsmcgee]

Check to see if you have power to the HSI, also some systems are ground sensitive. Make sure you have proper polarity and a good ground. If you have power to the ignitor ,if so, replace the HSI. No power to HSI, check board connection at jack plug or terminals. Check board at HSI terminals and see if power there, no power means board problem. Improper grounding of some systems will cause intermittent board failures and intermittent lighting. Hope this helps