I have a duo therm rooftop ac unit that is not working. The fan kicks in, but the compressor doesn't seem to even try to kick in. I'm assuming that I am going to have to replace the unit, but is there...
Could be the start capacitor. If you have two of the same units, you could swap the capacitors out and see if it helps. If you give it a go, be sure to discharge the capacitor before removing it.
I had the opposite problem - the blower motor would not start. A new capacitor got it going.