Ya iam going to say you got a bad t-stat
Yeah he may have got the cooler one by no fault of his own.
Some of the people that work at part stores are idiots.
They claim to hold an ase certification for parts pro but thruthfuly maybe only one person has that.
Just because they claim OEM does not mean that it is the same or even right.
I went to one part store to buy spark plugs for my 460 and they told me oem was ac delco
Needles to say I bought Motorcraft.
Kinda like the distributor I bought from a part store and the guy told me they do not sell bad parts.
The gear on the distributor was not in the correct place and I could not get it to seat properly.
I just about shoved it up his arse.
He told me I will order a new one I said no thanks since you are telling me the customer who is a trained professional that I am wrong.
I went to another part store and they told me yeah that happens all the time at that part store and he properly orded me one and it fit correctly.
So when I needed another one for another truck I went back to the part store that got me the defective free one and had no issues.