Our AC unit stopped working in July. I would guess that the unit is anywhere from 4-5 years old (since that's when the house was built) - we've lived in the house for almost 2.5 years and it's been working fine during that time. The home warranty co sent a HVAC tech out, who said the fuse had to be replaced. He replaced it and left, but it still wasn't working. Tech comes back, says its the blower motor. Blower motor gets replaced, tech leaves but unit still not working. HVAC co comes back, says it's the TXV valve and shows me how there's ice on the coils. When he went to replace the TXV valve, he discovered I have a R410A condenser but the air handler / evaporator coils are R22. He tells the home warranty that these are incompatible units and so now the home warranty won't cover it because of what he said. I had another company come out for a second opinion and also called several dealers / distributors myself and the second company and distributors / dealers say that I can put a 410A TXV on the current R22 evaporator coils and it will work fine. Do you agree? It's nearly impossible to look at the current TXV on there because of the positioning, but the people I spoke with all agree that it's probably a 410TXV b/c the system has functioned fine up to this point.

I have several questions:
Should I replace just the bad TXV with a 410A TXV or should I replace my current coils (replace current R22 coils with R410A coils)? Does anyone know what the price difference / range would be for replacing just the TXV vs new coils? Is there a performance difference R22 - R410 vs R410 -R410? One company was trying to tell me that I should just replace the entire coils since R22 coils are likely older than R410 condenser.

Any recommendations for what I can do to get the home warranty / HVAC co to reconsider? I've faxed the home warranty the second opinion but I don't if the language is strong enough for them. I can't seem to find anything authoritative on line that says that R410A systems can function with aR22 coils as long as there's a 410A TXV in place. I also called the HVAC company to ask them to reconsider their opinion and they said they would call the distributors / dealers I spoke with but I still haven't heard anything. Based on their past performance I'm not sure they are professional enough or care enough to follow up (they have been diagnosing since July 18th!).

Also, what are the opinions on Tempstar? I saw many questions about Goodman, Trane, Rheem / Rudd but barely any on Tempstar.

System info:
Tempstar Model No. EDM2X60JA2
Condenser / Compressor: N4A460GKB300

Thank you!