It's not running constant that you have to worry about. The worst thing for an A/C unit, or any piece of equipment, is constant starting and stopping. That's where you get most of your wear and tear.


Some t'stats will allow you to adjust your drift band. That's when you set it at 74F, but it doesn't come on until 75F and doesn't shut off until 73F. That's a 2 degree drift band. Sometimes those things come set to only have a 1 degree drift band (comes on at 74.5F and shuts off at 73.5F). That helps with comfort, but it greatly increases the number of times your A/C unit will start and stop. Increasing that drift band, if you can, goes a long ways to extending the life of your A/C unit.


The sudden change from maintaining your indoor temp to not even working at all still has me thinking the compressor isn't running. I'd still check that first. If it is and you're not getting cooling, turn the unit off. It means you are low on coolant which also means you're low on oil for the compressor. But when it comes to checking for and sealing leaks, it's best to let the pros do that. They can be impossible to find, and you and I don't really have the proper tools to draw a vacuum in the system and refill with the proper amount of refrigerant.