Outdoor AC unit won't turn off unless i flip the breaker, doesn't respond to thermostat.

Off all winter (northern USA), turned it on to no response. Reset it by flipping breaker off/on. It now stays on unless i flip the breaker. Note that it wasn't tripped.

I used the thermostat to turn it on/off but no response - at this point the AC tripped with a spark in here (and this didn't trip the house breaker). I checked over everything visually and see no noticeable damage, no wires or contacts are loose, the large fuse box isn't blown, and i cleaned out the grill pretty well.

Its blowing slightly cooled air - its not just moving air, it is cooling - and doesn't respond to thermostat.

I reset my thermostat and replaced the batteries and reset it again and so forth. I don't have any known issue with my thermostat and it controls the fan and heat correctly.

I've looked at a number of posts and websites/questions. The overwhelming number of solutions involve cleaning, resetting, fuses.

The things i haven't checked are the condenser and relay.

I'm going to get a tech to come for a tune up and ask what's going on.

Meanwhile, what would i check next while i wait?