Also you are failing to consider the double oven and microwave oven that actually did work. When buying appliances off craigslist that have been pulled out where you can’t test them you should have discounted your offer to reflect this risk. But pretty much it is understood that you are buying them as-is. He can claim
(falsely) your install caused the malfunction somehow. Hopefully you didn’t pay too much for the whole lot. You may want to negociate with him one more time and threaten to bring a small claims lawsuit and see if he bites but for $100 it isn’t worth anyone’s time and he might tell you to bring back everything and get your money back. Chaulk the $100 loss to experience and test before you buy or offer to buy them at a huge discount explaining to the seller your offer entails the risk that it might not work. All it all it doesn’t sound you are losing money because a double oven, microwave and dishwasher cost about $2000-$3000 new and you should have paid about $400 used for the whole lot less if it was not stainless/