Heat Pumps and Electric Heating - bad TXV on outdoor

So what exactly can go wrong with a TXV? My brand new Trane unit has already had the TXV on the outdoor unit replaced once - today I had the 3rd technician take a look at things since my outdoor unit isn't coming on anymore - diagnosed with a faulty thermostat that was not allowing the first stage heat to come on - it went straight to aux strips since the heat pump never kicked in. It was 60 degrees here today - he said that my TXV was frosting on the outside unit during the heating cycle and that it shouldn't do that when 60 outside. He assumed it was going bad. I mean, I understand coincidences, but to have 2 bad TXV's in less than 3 months? Is there some underlying fault that could be causing my TXV to fail prematurely? I know I just have a cursed system, but this is getting ridiculous. $8500 later I have a brand new heat pump system that hasn't worked longer than 2 weeks without something screwing up. And this has been going on since the week after Thanksgiving.

Thanks for any help on what could be causing the failed TXV on the outdoor unit.

TXVs rarely fail as long as the system is kept CLEAN and DRY during installation. Sounds like there has been some sort of contaminate introduced into the system at some point. I wouldnt knock Trane on this one since it does not sound like an equipment problem. I truly believe you are the victim of a very careless installer.

Thanks for the info Thermo - I know you have followed my whole story and we both know I had a very poor installation. The good news is, I have moved on from the first installer. And think I found a good guy yesterday. I just hope that if this guy does a clean install on a new TXV (assuming it gets to that point) that the contaminant isn't still in there to screw up another TXV. I guess time will tell.

I really don't mean to poo poo Trane constantly, but it seems like when people on these boards don't put down the manufacturer, that is the first question that always gets asked...make and model. But so far when the unit is running, it does a great job. And can't fault them on a bad thermo either.

Thanks again.

if there is junk in there, they need to change the filter (in the refrigerant line) and flush and clean the rest of the lines. or it could just come back again and clog the next one

It is common for residential a/c units to originally come equipped with a strainer rather than a filter/drier.
A properly sized filter/drier should have been installed along with the replacement expansion valve in addition to pulling a complete vacuum on the system prior to recharging refrigerant.
You would know a vacuum was pulled if you saw the technician connect a pump to the system through his guages and leave it running untill fully evacuated.
The way to know a proper vacuum is pulled is with an electronic guage that measures vacuum.

This is great info you all - thank you - if the TXV does in fact fail, I'll be sure to ask/watch and make sure the tech does these things. I do remember them pulling vacuum on it previoulsy (we also suspected a refrigerant leak) and remember them talking about a drier - but don't know the order in which these things were done or if they were even done on the same visit. There were so many visits... I'll ensure it is all done if this TXV fails.

Thanks again!

Im sure they pulled a vaccum and changed the filter/drier. If they dont normally do this, they will not be in business long. When I was just a young HVAC boy, I cut a few corners thinking I could change the laws of refrigerants and Murphy hit me in the face. What can go wrong will go wrong. I may overdo things a bit now but I sleep well at night knowing the system is working.