Hopefully the seller will "do the right thing"..
I can "do" this one! I'm not aware of the specifics of NY or NJ law, only a few of the Midwestern states...but I bet my answer will hold true there too, since all the state laws are based either on common-law practice, or on recent increases in "consumerism."
1. Seller has a liability (under statute, not derived from common law) to disclose known defects in the HVAC systems. This he APPARENTLY has done, at the appropriate time. See #6...
2. Seller is not required to be a mechanical engineer nor to be an HVAC contractor, and thus he is not required to know exactly what the repair of the (disclosed) problem entails...nor is he required to make a fully accurate diagnosis. He is only required to disclose that there is a problem of which he is aware.
3. The onus of fully inspecting and diagnosing the problem is on the buyer, during the inspection "window" of the sales contract. The buyer typically will share reports and estimates with the seller and request either that seller remedy the problem, give buyer a repair credit at closing (which may or may not be escrowed.)
4. Once the parties have AGREED on an approach (usually in writing) and a dollar amount, if the seller PERFORMS the agreed actions... any unresolved problems pass to the
buyer at the closing. Everything is geared toward the idea that when the parties walk away from the closing they are done with each other.
5. So in your case Wizer... it depends on who did the inspection and what the specifics are of your agreement with the seller. If it's the case that you had a licensed HVAC contractor inspect the problem and he blew the diagnosis, you may have some recourse against HIM. And that's better than you'd do if he was an eye doc and misdiagnosed you...LOL...
But unless the seller gave you a written "blanket assurance" that he would FIX the problem (regardless of the cause and regardless of the cost) you probably have gotten all you're gonna get from him.
6. The only exception to that is
fraud on the Seller's part. IOW, if you can find the contractor who CORRECTLY diagnosed the problem for the seller....information the seller FAILED to disclose... and THAT contractor will so testify or affirm ...then you have Mr. Seller by the short hairs and you can probably get the whole thing paid for and recover something more for your time and trouble. That's more likely to happen in a small town where you only have a handful of contractors.
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It was simpler 20 years ago...the only rule was "CAVEAT EMPTOR." And when you bought property you got what you got.