[XE1100cycle]

I have a Trane XE 1100 system manufacture 11/98 that cycles too frequently. I have tried two different thermostats (old mercury style and new programmable) with no differnce in cycles, cleaned/replaced filter, cleaned all coils, verified no windows or doors are left open. The t-stat can be set to 74 and reach the needed temp, compressor turns off and 7 minutes later the compressor turns on for a five minute cycle and repeats this too frequently. I can even adjust the temp to 76 at night and the cycles continue throughout the night and the indoor temperature is at approx. 72-73*. I am not sure but something is telling the compressor to turn on no matter what the t-stat is set to. Is there anything to check for this? Needles to say my power bill has increased over the last 2-3 months since this has started.