I went out last week on a 2yr old Trane dual fuel system. We got the call cause the original Trane dealer went out of business and my coworkers wife is this lady's boss.
So she tells me the hp never seemed to heat very well. The air coming from the vents seemed cool.
I go around and find this.

I flip disconnect to check cap. I find one leg still hot. Pull cover off disconnect and find one leg direct wired. Disconnect will now not reset. So I direct wire other leg and check operation.
I find the fan motor going out. I get it moving but its slow. Looking at the fan motor I see its an aftermarket Wagner motor. Definitely not original.
Check press and can tell its low on charge.
I order the correct motor from Trane.
HO says she has not had any work to it. Only called the original installer cause the hp didn't seem to heat well. He told her it was working fine.

I went back out today. Replaced the disconnect and fan motor. I recover the remaining 4lbs. I weigh in the factory charge of 9lbs. and some dye to leak check.

In cooling mode looks good. 23 degree TD. Can't remember press. It was cool out.

Switch it to heat mode. Press 300/36. Discharge line 196. Return line 77-78 degrees. 76 other side of biflow drier. 6 degree temp rise. Outdoor txv freezing up.
Going back with an outdoor txv and drier.
Btw, I found the leak. The installer didn't get the line sealed at the indoor coil.

Apparently he tried getting rid of all of his scrap copper. How many joints do you see?

Found out later that not only did this dealer shut down, he skipped town on his debts.

Who says hacks can't install Trane.