Yes, I have a trane XL1100 model number YCX036F1M0B. The airconditioning unit is working but not the heater part. The thermostat control will turn on the fan but the spark initiator will not click on and the gas valve will not open. I opened the panel to the electronic controls and is has a red light that flashes 2 times. According to a Ign diagnostic indicator chart provided with the unit it means there is s system lock out ( no flame ). What can cause this system lock out. I have looked through the internet and found there are several people having this same problem with this same unit by trane. I am assuming there must be a design flaw or something having to do with a annual or a periodic maintenace routine we are all not doing. I would really like to know how to go about fixing this problem as we are elderly couple living on a fixed income and would try to solve this problem on our own with some help and not have to call in a professional hearter repair man. Can it be done, fixed I mean and how do I do it?

Could be as simple as a dirty flame sensor. Interrupt & restore power supply to cancel lockout, then observe operating sequence from start-up. Post back with your observations. HVAC1000, here's another cha-ching opportunity... :p