It's probably too cold. Remove the front louvered cover to expose the cap tube. The one from the stat. remove the rubber bumper from the front coil and pull the cap tube from the rubber. Hold the cap tube in your hand until you feel that the tube is pretty warm. then turn the unit on. How long does it run ? If the stat is a snap action one find yourself a portable heater with a fan, an old car warmer will do. Have it pointed to the area of the stat. Let it get good and warm. How long does it run ?

Wow, just wow! Okay- so here's what I know. When a service person comes out they need to operate the unit to be sure it's operating correctly before they leave. Period. You can't say it's fixed if you don't. If not, it's on them. Technicians want to be paid like a professional. I get that. However that means they need to be properly trained, and have professional workmanship. Far too often, particularly with AC/Heat pump techs that's simply not the situation. For $900 you should have received stellar service. The balance of the original warranty is a common situation. I hate compressor replacements! Too often the tech doesn't have the skill level, the system doesn't get cleaned up well, it doesn't get charged correctly and it turns into a mess. Bad TX valve?!? No way that should have gotten past him when the compressor was replaced! Or was it that he didn't clean up the system? I would refuse to pay for this call - that it should have been done right the first time they were there.

Ok, I really do doubt that lint is the cause of the failures, unless the unit was really plugged up by the lint. Ask the diagnosing tech what the head pressure was when he thought the coils were plugged up, and what the outdoor ambient temp was, if he doesn't know then get another tech. Pressure and temperature measurements are the only way to properly diagnose refrigerant related problems, including plugged coils. I would suspect that the first compressor that burned out contaminated the sealed refrigeration system with acids. Here is what happens, when a sealed compressor motor burns out the internal windings overheat and burn off the varish, in the presence of refrigerant, oil, and heat very strong acids are formed. When the compressor gets changed out the acid eats away at the varnish that coats the motor windings of the new compressor. Back in the old days R-11 was used to flush a system out that had burned out a compressor to remove the acids. Today environmental laws prohibit that practice. Here is what should be done to prevent future burn-outs. A removeable suction filter dryer that is made just for system burnouts should be installed just before the compressor. The system should be allowed to run for week under normal use, then the tech comes back and changes the suction filter. A month later another change occurs, and at three months an acid test is done on the oil to assure that all acid has been removed. At this point if all the acid is gone either another suction filter is put on, or the pipe is spliced back together with flare fittings leaving the filter out entirely. Unless a proper burnout cleanup is made you will continue to be replacing compressors on a frequent basis. Most compressors can live 10 years or more if they are installed correctly in a system that is not contaminated with acids from previous burnouts.

I don't know that I would say that Builder's grade is an unofficial term. Many different manufacturer's use the term although many manufacturer's model numbers do not go to the extent that Trane does in listing this nomenclature within the model # of the unit. (I know this because of decades of being in this industry. This doesn't mean if you buy a new home that it won't contain a non-builder grade unit.... it depends greatly who is making these kinds of decisions.) Quality wise builder's grade is very low. In some cases even the compressors have cheaper parts and or where they were made is likely 3rd world like China. Since Ingersol Rand bought Trane Company many years back the only thing I really know for sure -- the units are only assembled in USA. With that said, Trane has a compressor manufacturing facility in Mexico and the China location is rumor. Given that Ingersol Rand is international company, the China location very well could be fact. Given the low end nature your AC condenser, I would run it and not worry about rust. It simply would not be worth the risk to mess with it. Typically major name brands use the nomenclature of Builder Grade. Many times the major names want you to buy one of their branded brands when the builder grade fails. It's merely a form of brand recognition to keep selling products. Off brands or brands that you rarely hear about are often considered value brands, some not all in my opinion are better than the builder graded brands. These brands aren't called builder grade for obvious reason... builders don't use them. This is where builder grade name comes from. Builders move a lot of units (complete systems), this is another piece of the puzzle that major name brands want... they are only here to sell systems. So to get the accurate picture you have to take a step back as to why it is the way it is. There are only 7 HVAC manufacturer's in USA a non major brand name OR off brand name unit... where do you think it comes from? Hint: The same line the major name brand comes from... in some cases the brand decal mounted to the unit is the only difference. I can tell you Trane / American Standard is odd ball out, simply because they manufacture their own compressors. Nearly 90% of USA condensers use Copeland Scroll, manufactured by Emerson. Which should tell you if the unit has a Copeland Scroll in it, there is very little difference from one brand to another. Put another way to help you understand: A builder is building you a home, he says I'm going to install a 'whiz bang - HVAC brand'. You say: I've never heard that brand before, and so there's concern and a lot of fuss the contractor will be dealing with. Now that same builder says: I am going to put in 'Trane' brand HVAC system for your new home. Ok, wow that's a name I know. He doesn't tell you it's builder grade unit. It's still a Trane brand. But he doesn't have the backlash of having to ease your concerns of a brand you never heard of. The manufacture gets even more brand awareness from home owner. Trane sells the builder grade unit for a $100 or $200 cheaper per system to builder. Builder builds 1,000 homes --- the more money builder cuts from materials the more the builder makes in profit. If he saves $200 per unit --- 1000 homes --- $200,000 simple math.