HVAC is where my career began after the Navy...I assume you had a split system heat pump system installed. (A condenser unit outside and air handler inside)..The other option(s) would be a package unit where everything is in one unit outside...$6500 sounds kind of high to me unless you had duct work installed, but I have been away from Florida for quite some time too...

 

If the contractor fails to "make it right" the only recourse really is to have another company fix the problem...It shouldn't void the warranty...It's not a requirement that the same company that installed the system do all the work on it. Now if the leak is the fault of the contractor such as crappy solder joints or improper installation, the warranty doesn't cover that so you would have to pay the other contractor for that and then try and recoup the total you paid to the second contractor probably suing him...Some contractors might find some sort of terminology to use to describe the work being done to satisfy the manufactures warranty since the first few years covers both parts and labor (generally 5 years parts and labor and 10 years parts)...

 

The leak could be in the a/c coil in the air handler,the condenser coil, the service valves, or any solder joint inside the units done in the assembly of the units, which would be covered by the warranty no matter who fixes it...

 

It's odd the contractor doesn't seem to want to fix it, since it should be under warranty

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