The last post is definitely on the money, many compressors are replaced needlessly. Mon a homeowner had been told his compressor was burt out and a new one was needed. was also told condensing unit was junk and fan motor burnt out waa advised to replace whole unit. We were called because the company quoted him a whopping price, 3500 for the job. Checked unit, fan motor was burnt out, checked compressor, compressor, windings checked ok. Unit was an older Lennox that used both a start and run capacitor. Both were bad, I learned later after repairing unit and talking to home owner that there had been a power outage in the are, a tranformer was located right behind house, apparantly some type surge had knocked the stuff out. A neighbor also had furnace trouble, the main control board was fried on his. We called the power co and they are investigating. So be very sure your compressor is bad before opting for a new one.

It's most likly to be restricted airflow. Cause can range from dirty filter,dirty evap coil,collapsed return to blower not moving suffecent air. Did ambient outdoor tempature in your location drop recently? While waiting for tech to return I suggest raising temp setting to highest point at t-stat and setting fan to ON/CONT. After 6 or more hours set temp for normal operation but leave fan set ON/CONT. Carfully test volume of air flow at the start and each hour or two.

I got it working! Funny story.... At dovetails' suggestion, I contacted Trane Canada. It wasn't clear on their website whom the appropriate contact would be, so I emailed the service manager for the Northwest. He called me back immediately. Said he was actually with the Commercial division but thought he could help me. I told him the thermostat was fine but he had me check it anyway. It is fine. I told him my husband checked the circuit breaker and it is fine. He had me check it anyway. It didn't look tripped but I switched it off and on anyway. I go outside.....and hear the sweet, sweet sound of my compressor working! I'm going to razz my husband -my engineer husband - real bad when he gets home to this lovely cool house on this 30 degree scorcher day. To be fair, I didn't think to check it and switch it off and on myself. The Trane guy said sometimes when it's tripped the switch barely moves and you can't tell just by looking. I learned a new skill today. Thanks for all your input and to dovetails for suggesting contacting the manufacturer directly. Unfortunately my neighbour will be most unhappy about this development. He harassed me all last summer over the noise from the compressor (I believe ours is one of the quieter models) and it is below the city bylaw for daytime use. I got to know my bylaw officers very well last summer. Fortunately they realize he is the unreasonable one. Every time I turned on AC he would park his lawnmower or some loud power tool beside his fence and run it without using it. It was always many decibels louder than my AC. He has kicked around a bag of glass bottles? slammed his garage door repeatedly, anything to create a disturbance. He's yelled at me to "shut that F...ing thing off!" He's unsuccessfully tried to engage other neighbours in his campaign. One time he flashed a bright spotlight on my bedroom window. He's been defiant with Bylaw that if I can use my AC, he can make whatever noise he wants. They appear to little clout to stop him. They wanted to lay a charge against him and take him to court. Then the city attorney called me and said he wouldn't waste resources taking to court a "dispute between two neighbours" as though I have done something wrong too. This neighbour has done all of this being well aware that my AC was prescribed by neurologist as a medical device due to the debilitating effects of heat on my multiple sclerosis. Here we go....... Thanks again everyone!

Extremely unlikely because as the guy said... eventually the unit starts and runs fine. Voltage drop = no run. "If voltage drop occurred while unit was running... it would not stay running." No where does OP say anything about unit cutting out while after starting and running. You have to know what you are talking about to come to such conclusions. LOL. Does a car keep running if there is no gas? Can a car be hard to start, but then run fine once started? Yeah ok, common sense. While a car is a poor comparison more people understand the operation of a car than anything else I could use as an example. voltage drops tend to stay, not magically disappear and reappear. But thanks for playing.... In over 22 years of diagnosing only 1 voltage drop problem... if you have a voltage drop you will know it quite easily. (More complex problems in regards to start up? Uh no. Guess again and again and again.) More common to drop a leg from the pole... while also rare that's happened about half dozen times in 22 years of running service. Central AC Unit won't start with only 120v available, that confuses people because some things inside the house will still operate normally as long as it doesn't require the full 240v to operate. In Vegas, they give you odds... in a forum board that's also what I give. Magic 8 ball --- out.