[Adapted from part of a din Torah.] Reuven sold his car to Shimon (who paid immediately) and was to give the car to Shimon a week later. When Shimon received the car, the air conditioning was not working. Reuven apologized and said that his garage had promised to fix it already and that they would do so within a few days. Shimon wanted to back out, but Reuven refused to return the money, and they started exploring dispute resolution venues. In the meantime, Shimon used the car. After 16 days and aggravation for Shimon, it was fixed. Even though the car now works well enough, Shimon still wants his money back. Does he have a right? Answer:
The lack of an air conditioner in a car these days in a hot country is considered a flaw that is grounds for mekach ta’ut (misinformed sale) and bitul mekach (nullification of sale). However, several elements might preclude bitul mekach.
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The Rambam (Mechira 15:3) and Shulchan Aruch (Choshen Mishpat 232:3) rule that one is not able to claim bitul mekach due to a flaw if he used the object after discovering it. In this case, Shimon used the car after finding out about the flaw.
On the other hand, we need to look at why using the object precludes bitul mekach. The Rambam (ibid.) explains the halacha as being based on presumed mechila, i.e., if he uses it, apparently he waived his right to return it. This case, though, is apparently different in that he previously stated explicitly that he wants bitul mekach. In fact, the Ritva (Bava Metzia 50b) says that if one grossly overcharged to the extent that the buyer can invoke bitul mekach, he can do so even after using the object, if he previously informed the seller of this intention. The simple explanation is that using the object is an apparent indication of mechila, but a clear statement that he is not mochel makes that indication irrelevant. In this case, Shimon demanded bitul mekach and did not rescind that demand. The Pitchei Teshuva (ibid.) cites a machloket whether the Ritva’s extension of the ability to do bitul mekach applies only to mekach ta’ut due to mischarging (Galia Massechet, CM 10) or even based on flaws (Machaneh Ephrayim, Ona’ah 5), as in our case
Furthermore, the Pitchei Teshuva (CM 232:1) posits that if extenuating circumstances forced the buyer to use the flawed object, he retains the right to back out later. In our case, it is unreasonable to expect Shimon, who already paid for a car and did not have the money returned to buy another, to not use the car. In a case like this, where Reuven permits Shimon to use the car even though he knows Shimon still wants bitul mekach, the Galia Massechet should agree (the analysis of this point is long). He clearly does not mean to be mochel and he clearly is not stealing by using it.
But there is a counter indication. By the time the question reached beit din, there no longer were grounds for mekach ta’ut, as the air conditioner was fixed. Still, this does not make a difference for the following reason. When there is mekach ta’ut without mechila, the sale had never been valid (see Galia Massechet ibid.). Therefore, since there is no agreement or kinyan after the air conditioning was fixed, Shimon does not have to go through with such a cancelled agreement, whatever his reasons are.
Despite the above, we believe that Shimon cannot back out. The Shulchan Aruch (CM 232:5) says that a flaw that can be readily fixed does not nullify a sale; rather, the seller has the right to pay for it to be fixed. The Rama (ad loc.) elaborates on this distinction, but his language creates some confusion. He says that the seller can stave off bitul mekach when the flaw is not in the sales item’s "physical essence" and the item does not lose its normal name. An example in which the seller cannot demand to fix a house is a when it has an insecure wall. Although one could argue the point, we posit that a car that has an air conditioner, just that it needs fixing, is one that the seller has a right to fix in a timely fashion (elaboration is beyond our present scope).