Air Conditioning - Trane XE1000: outside unit will not run.

Over the past three years we've been noticing the A/C has been running longer and longer in order to cool the house. The system is 12 years old and has been running great otherwise. I've checked the coils and they are all very clean. I clean the outside coils every couple years. I put new capacitors in the inside blower unit and the outside. But the outside unit still will not run. It did run for a few minutes when I checked it a few weeks ago but now that it is hot outside it is not running. I've checked all the breakers and everything is on. The little light on the outside panel blinks once every second just like it always did. Is it possible that the outside unit would not run if the freon got very low? The system has not been running over the winter and perhaps the freon has gotten very low.

UPDATE: I got it running by moving the switch on the thermostat between OFF and COOL a bunch of times. So would this maybe mean the contactor needs replacing? Also, the cooling is very minimal. The big pipe at the outside unit feels just barely cool and the small pipe feels only slightly warm.

Can be the tstat there first. Might jump from R to Y and see if that starts the outdoor unit. If not then check the contactor in out door unit. does it get 24V?? is it bad?? contactor points bad.

The big pipe at the outside unit feels just barely cool and the small pipe feels only slightly warm.
sure sounds low on freon.;) yes some have a low pressure cut out in them