IMO the fact lines were not installed right to begin with call's contractor's reliability into question. If that wasn't enough to warrant a contractor change,it took "numerous visits" before he figured it out. Since you are paying for correcting his mistake,call someone that know's what they are doing. Something else to consider is with construction stirring up dust filter would have quickly clogged and someone might have removed it causeing ducts and coils to become clogged. All that is guessing at best but you furnished me next to no details to go on.

not enough factual information provided from OP to make an informed comment...what exactly is the problem/symptoms that point to a problem with lineset?...who is telling you the problem is the lineset-the contractor or the dealer who installed the job?...

IMO

why was the AC 'freshly' installed? was the other one stolen? To many things to guess at when it comes to a foreclosed property.

# The devil is in the details.

It was indeed stolen. The property was bank owned and they had to get it to a habitable state to sell to regular homebuyers so installed a new one. The problem is the contractor installed a brand new air handler, thermostat and condenser onto an existing drain line and lineset. The AC apparently worked while being tested and was then left as a completed job. I bought the house and started the rehab. Straight away it kept cutting out or blowing warm air. It turns out the drain line was clogged which stopped condensation draining so a float switch kept cutting out (this took a couple of visits and a new float switchto figure out). But there also seems to have been a second problem with the line set, as whatever work is done (so far a new float switch, new second condenser, a new second compressor, a new evaporation coil...) it hasn't fixed the problem of the ac running and running and blowing warm air.

My question is, am I expected to pay for a new lineset if he installs one as another attempt to fix this 4 month problem? So far it has all been under warranty.

I am unconvinced that the lineset is the problem. Of course you have not mentioned models of air handler and condenser that were installed. After several attempts, I am not certain that this dealer can solve your problems. I suspect bank went bottom fishing when this system was installed. Lineset must be sized correctly to system and manufacturer specs. Does dealer intend to reuse refrigerant or pump fresh refrigerant?...has new system been properly registered for warranty? Offer to split the cost of the new lineset install. That seems reasonable. Dealer should have some skin in the game considering problem has not been solved.

IMO

Most of what you are telling us doesn't hold water. I doubt you will find answers with all these thin storys. For example,who steal's an air handler? Example #2, why would a contractor install an air handler,evap coil.condenser unit and t-stat without installing a new line set if one is needed? ASking questions on the net is no subsitute for a compitent contractor,find one.

Klem,

This is a bank owned foreclosure. The banks don't do home renovations, they are the servicer of the loan, their only interest is MONEY. Either to protect it or recoup it.

To the OP:

Installers are 'sometimes' the cheaper of the two when it comes to HVAC installation. But installers have very little in the way of technical ability to diagnose what can be complex problems of the refrigeration circuit.

Refrigeration line sets are reused all the time with little fan fare. The requirement is that you 'know' what you are doing.

With all the problems the OP has had I think it's easy to assume that someone doesn't know what they are doing. Now who do you suppose that is?

You can either accept it and cut your losses or continue to go down the trail of tears.

It's very easy to play the blame game... oh today we'll blame the line set. Tomorrow we'll blame the drain line. The next day we may blame the manufacturer. ( Bash or Blame doesn't matter, it's typically the same thing.)